[clang] [clang] Rename diag notes that assumed precompiled dependencies are pch's, NFCI (PR #142161)

[Cyndy Ishida via cfe-commits]

cyndyishida wrote:

Seems like we're ok with "precompiled file" in terms of a generalization of both precompiled headers & module files, when it's applicable, in diagnostic messages. I am going to merge this and handle aligning the rest of the diagnostics in a follow-up pr.

https://github.com/llvm/llvm-project/pull/142161