[clang] Don't typo-fix an expression in a SFINAE context.

If this is a SFINAE context, then continuing to look up names
(in particular, to treat a non-function as a function, and then
do ADL) might too-eagerly complete a type that it's not safe to
complete right now. We should just say "okay, that's a substitution
failure" and not do any more work than absolutely required.

Fixes #52970.

Differential Revision: https://reviews.llvm.org/D117603