[clang-tools-extra] [clangd] Fix the modification detection logic in `ClangdLSPServer::applyConfiguration`. (PR #115438)

[Nathan Ridge via cfe-commits]

https://github.com/HighCommander4 approved this pull request.

Thanks, this LGTM.

It would be nice to have a test exercising `applyConfiguration` itself, but I realize we don't currently have such tests (and that the intended effect -- that an open file whose command did not change does **not** get re-parsed -- is not trivial for check for).

It someone would like to contribute such test coverage in a future patch, that would certainly be welcome.

https://github.com/llvm/llvm-project/pull/115438