[clang] [clang][lex] Fix lexing malformed pragma within include directive (PR #138165)

[Shafik Yaghmour via cfe-commits]

https://github.com/shafik commented:

Thank you for the fix, this needs a test and release note. 

Release notes for clang are in `clang/docs/ReleaseNotes.rst`.

I am not sure what the right file for testing is though @AaronBallman 

https://github.com/llvm/llvm-project/pull/138165