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

[Victor Chernyakin via llvm-commits]

localspook wrote:

To make it so that the linked issue is automatically closed when this PR is merged, you should have in your PR message the phrase "Fixes #161939". GitHub [won't understand it](https://docs.github.com/en/issues/tracking-your-work-with-issues/using-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword) if you write it as "fixing issue #161939".

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