[clang-tools-extra] [clang-tidy] fix `bugprone-narrowing-conversions` false positive for conditional expression (PR #139474)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-aarch64-quick` running on `linaro-clang-aarch64-quick` while building `clang-tools-extra` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/65/builds/20669

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'Clang Tools :: clang-tidy/checkers/bugprone/narrowing-conversions-conditional-expressions.cpp' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
Running ['clang-tidy', '/home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/tools/clang/tools/extra/test/clang-tidy/checkers/bugprone/Output/narrowing-conversions-conditional-expressions.cpp.tmp.cpp', '-fix', '--checks=-*,bugprone-narrowing-conversions', '--config={}', '--', '-std=c++11', '-nostdinc++']...
------------------------ clang-tidy output -----------------------

------------------------------------------------------------------
------------------------------ Fixes -----------------------------

------------------------------------------------------------------
FileCheck -input-file=/home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/tools/clang/tools/extra/test/clang-tidy/checkers/bugprone/Output/narrowing-conversions-conditional-expressions.cpp.tmp.cpp.msg /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang-tools-extra/test/clang-tidy/checkers/bugprone/narrowing-conversions-conditional-expressions.cpp -check-prefixes=CHECK-MESSAGES -implicit-check-not={{warning|error}}: failed:
FileCheck error: '/home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/tools/clang/tools/extra/test/clang-tidy/checkers/bugprone/Output/narrowing-conversions-conditional-expressions.cpp.tmp.cpp.msg' is empty.
FileCheck command line:  FileCheck -input-file=/home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/tools/clang/tools/extra/test/clang-tidy/checkers/bugprone/Output/narrowing-conversions-conditional-expressions.cpp.tmp.cpp.msg /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang-tools-extra/test/clang-tidy/checkers/bugprone/narrowing-conversions-conditional-expressions.cpp -check-prefixes=CHECK-MESSAGES -implicit-check-not={{warning|error}}:


--
Command Output (stderr):
--
/usr/bin/python3.10 /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang-tools-extra/test/../test/clang-tidy/check_clang_tidy.py /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang-tools-extra/test/clang-tidy/checkers/bugprone/narrowing-conversions-conditional-expressions.cpp bugprone-narrowing-conversions /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/tools/clang/tools/extra/test/clang-tidy/checkers/bugprone/Output/narrowing-conversions-conditional-expressions.cpp.tmp -- -- # RUN: at line 1
+ /usr/bin/python3.10 /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang-tools-extra/test/../test/clang-tidy/check_clang_tidy.py /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang-tools-extra/test/clang-tidy/checkers/bugprone/narrowing-conversions-conditional-expressions.cpp bugprone-narrowing-conversions /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/tools/clang/tools/extra/test/clang-tidy/checkers/bugprone/Output/narrowing-conversions-conditional-expressions.cpp.tmp -- --
Traceback (most recent call last):
  File "/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang-tools-extra/test/../test/clang-tidy/check_clang_tidy.py", line 399, in <module>
    main()
  File "/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang-tools-extra/test/../test/clang-tidy/check_clang_tidy.py", line 395, in main
    CheckRunner(args, extra_args).run()
  File "/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang-tools-extra/test/../test/clang-tidy/check_clang_tidy.py", line 306, in run
    self.check_messages(clang_tidy_output)
  File "/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang-tools-extra/test/../test/clang-tidy/check_clang_tidy.py", line 267, in check_messages
    try_run(
  File "/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang-tools-extra/test/../test/clang-tidy/check_clang_tidy.py", line 62, in try_run
    process_output = subprocess.check_output(args, stderr=subprocess.STDOUT).decode(
  File "/usr/lib/python3.10/subprocess.py", line 421, in check_output
    return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
  File "/usr/lib/python3.10/subprocess.py", line 526, in run
    raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['FileCheck', '-input-file=/home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/tools/clang/tools/extra/test/clang-tidy/checkers/bugprone/Output/narrowing-conversions-conditional-expressions.cpp.tmp.cpp.msg', '/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang-tools-extra/test/clang-tidy/checkers/bugprone/narrowing-conversions-conditional-expressions.cpp', '-check-prefixes=CHECK-MESSAGES', '-implicit-check-not={{warning|error}}:']' returned non-zero exit status 2.

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/139474