[clang][lex] NFCI: Use FileEntryRef in Sema::CodeCompleteIncludedFile

This patch replaces some calls to the deprecated `DirectoryEntry::getName()` with calls to `DirectoryEntryRef::getName()` in SemaCodeComplete.cpp.

Depends on D127654.

Reviewed By: bnbarham

Differential Revision: https://reviews.llvm.org/D127658

GitOrigin-RevId: b1e5b28b8c4d8af294906ee27a62b28079d3f337
1 file changed