[clang] Revert "[clang] fix matching constrained out-of-line definitions of class specialization member function templates" (PR #193558)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `intel-sycl-gpu` running on `intel-sycl-gpu-01` while building `clang` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/225/builds/6490

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

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang :: SemaTemplate/concepts-out-of-line-def.cpp' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 1
/home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/bin/clang -cc1 -internal-isystem /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/lib/clang/23/include -nostdsysteminc -std=c++20 -Wno-c++26-extensions -verify /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/llvm-project/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
# executed command: /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/bin/clang -cc1 -internal-isystem /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/lib/clang/23/include -nostdsysteminc -std=c++20 -Wno-c++26-extensions -verify /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/llvm-project/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
# .---command stderr------------
# | error: 'expected-error' diagnostics seen but not expected: 
# |   File /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/llvm-project/clang/test/SemaTemplate/concepts-out-of-line-def.cpp Line 854: out-of-line definition of 'buggy' does not match any declaration in 'PackIndexExpr::TplClass<int>'
# | error: 'expected-note' diagnostics seen but not expected: 
# |   File /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/llvm-project/clang/test/SemaTemplate/concepts-out-of-line-def.cpp Line 845: TplClass defined here
# | 2 errors generated.
# `-----------------------------
# error: command failed with exit status: 1

--

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


```

</details>

https://github.com/llvm/llvm-project/pull/193558