[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-armv8-quick` running on `linaro-clang-armv8-quick` while building `clang,llvm` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/154/builds/22538

<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 'LLVM-Unit :: Support/./SupportTests/163/416' FAILED ********************
Script(shard):
--
GTEST_OUTPUT=json:/home/tcwg-buildbot/worker/clang-armv8-quick/stage1/unittests/Support/./SupportTests-LLVM-Unit-2689614-163-416.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=416 GTEST_SHARD_INDEX=163 /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/unittests/Support/./SupportTests
--

Script:
--
/home/tcwg-buildbot/worker/clang-armv8-quick/stage1/unittests/Support/./SupportTests --gtest_filter=ProgramEnvTest.TestLockFile
--
../llvm/llvm/unittests/Support/ProgramTest.cpp:571: Failure
Value of: Error.empty()
  Actual: false
Expected: true


../llvm/llvm/unittests/Support/ProgramTest.cpp:571
Value of: Error.empty()
  Actual: false
Expected: true



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


```

</details>

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