[clang] [NFC][clang] Remove superfluous header files after refactor in #132252 (PR #132495)

[Tomas Matheson via cfe-commits]

https://github.com/tmatheson-arm approved this pull request.

LGTM. Does this actually fix the build time regression from the previous patch?

https://github.com/llvm/llvm-project/pull/132495