[clang] [llvm] Remove GtestMatchers and GtestMatchersTest (PR #162524)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-ppc64le-linux-multistage` running on `ppc64le-clang-multistage-test` while building `clang,llvm` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/76/builds/13131

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

```
Step 5 (ninja check 1) failure: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
...
PASS: mlgo-utils :: corpus/extract_ir_script.test (102464 of 102473)
PASS: lit :: shtest-define.py (102465 of 102473)
PASS: LLVM :: tools/llvm-readobj/ELF/file-header-machine-types.test (102466 of 102473)
PASS: ThreadSanitizer-powerpc64le :: restore_stack.cpp (102467 of 102473)
PASS: LLVM :: tools/llvm-readobj/ELF/AMDGPU/elf-headers.test (102468 of 102473)
PASS: SanitizerCommon-lsan-powerpc64le-Linux :: Linux/signal_segv_handler.cpp (102469 of 102473)
PASS: SanitizerCommon-tsan-powerpc64le-Linux :: Linux/signal_segv_handler.cpp (102470 of 102473)
PASS: SanitizerCommon-ubsan-powerpc64le-Linux :: Linux/signal_segv_handler.cpp (102471 of 102473)
PASS: SanitizerCommon-msan-powerpc64le-Linux :: Linux/signal_segv_handler.cpp (102472 of 102473)
PASS: SanitizerCommon-asan-powerpc64le-Linux :: Linux/signal_segv_handler.cpp (102473 of 102473)
command timed out: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=2720.603607

```

</details>

https://github.com/llvm/llvm-project/pull/162524