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

[Cyndy Ishida via cfe-commits]

================
@@ -24,8 +24,9 @@ def err_fe_ast_file_modified : Error<
     DefaultFatal;
 def err_fe_pch_file_overridden : Error<
     "file '%0' from the precompiled header has been overridden">;
-def note_pch_required_by : Note<"'%0' required by '%1'">;
-def note_pch_rebuild_required : Note<"please rebuild precompiled header '%0'">;
+def note_ast_file_required_by : Note<"'%0' required by '%1'">;
+def note_ast_file_rebuild_required
+    : Note<"please rebuild precompiled file '%0'">;
----------------
cyndyishida wrote:

I don't feel that strongly but I don't see the value added to users seeing this diagnostic by adding "AST" to "file", and it requires less logic to qualify "module file" vs "precompiled header". My main goal is to avoid emitting an incorrect diagnostic.

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