[llvm] [NFC][ADT] Remove << operators from StringRefTest (PR #105500)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `bolt-x86_64-ubuntu-nfc` running on `bolt-worker` while building `llvm` at step 8 "test-build-bolt-check-bolt".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/92/builds/5001

Here is the relevant piece of the build log for the reference:
```
Step 8 (test-build-bolt-check-bolt) failure: test (failure)
******************** TEST 'BOLT :: perf2bolt/perf_test.test' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 5: /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/bin/clang /home/worker/bolt-worker2/llvm-project/bolt/test/perf2bolt/Inputs/perf_test.c -fuse-ld=lld -Wl,--script=/home/worker/bolt-worker2/llvm-project/bolt/test/perf2bolt/Inputs/perf_test.lds -o /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp
+ /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/bin/clang /home/worker/bolt-worker2/llvm-project/bolt/test/perf2bolt/Inputs/perf_test.c -fuse-ld=lld -Wl,--script=/home/worker/bolt-worker2/llvm-project/bolt/test/perf2bolt/Inputs/perf_test.lds -o /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp
RUN: at line 6: perf record -e cycles:u -o /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp2 -- /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp
+ perf record -e cycles:u -o /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp2 -- /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp
Lowering default frequency rate from 4000 to 2000.
Please consider tweaking /proc/sys/kernel/perf_event_max_sample_rate.
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.003 MB /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp2 (20 samples) ]
RUN: at line 7: /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/bin/perf2bolt /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp -p=/home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp2 -o /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp3 -nl -ignore-build-id 2>&1 | /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/bin/FileCheck /home/worker/bolt-worker2/llvm-project/bolt/test/perf2bolt/perf_test.test
+ /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/bin/FileCheck /home/worker/bolt-worker2/llvm-project/bolt/test/perf2bolt/perf_test.test
+ /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/bin/perf2bolt /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp -p=/home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp2 -o /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp3 -nl -ignore-build-id
/home/worker/bolt-worker2/llvm-project/bolt/test/perf2bolt/perf_test.test:10:12: error: CHECK-NOT: excluded string found in input
CHECK-NOT: !! WARNING !! This high mismatch ratio indicates the input binary is probably not the same binary used during profiling collection.
           ^
<stdin>:26:2: note: found here
 !! WARNING !! This high mismatch ratio indicates the input binary is probably not the same binary used during profiling collection. The generated data may be ineffective for improving performance.
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Input file: <stdin>
Check file: /home/worker/bolt-worker2/llvm-project/bolt/test/perf2bolt/perf_test.test

-dump-input=help explains the following input dump.

Input was:
<<<<<<
        .
        .
        .
       21: PERF2BOLT: waiting for perf mem events collection to finish... 
       22: PERF2BOLT: processing basic events (without LBR)... 
       23: PERF2BOLT: read 20 samples 
       24: PERF2BOLT: out of range samples recorded in unknown regions: 18 (90.0%) 
       25:  
       26:  !! WARNING !! This high mismatch ratio indicates the input binary is probably not the same binary used during profiling collection. The generated data may be ineffective for improving performance. 
not:10      !~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                                                   error: no match expected
       27:  
       28: PERF2BOLT: wrote 2 objects and 0 memory objects to /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/tools/bolt/test/perf2bolt/Output/perf_test.test.tmp3 
       29: BOLT-INFO: 2 out of 13 functions in the binary (15.4%) have non-empty execution profile 
>>>>>>

--

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


```

https://github.com/llvm/llvm-project/pull/105500