[clang] [Clang] Fix `-Wsign-compare` assertion when negating a vector of unsigned integers (PR #223295)

[Shafik Yaghmour via cfe-commits]

https://github.com/shafik commented:

I saw you mentioned `matrix_type` in the summary, are they affected by this change, if so that should be tested. 

https://github.com/llvm/llvm-project/pull/223295