[clang] [Clang] Refactor uses of `Cand->Function` in SemaOverload.cpp (PR #98965)

[Shafik Yaghmour via cfe-commits]

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@@ -11846,19 +11854,21 @@ static void DiagnoseFailedEnableIfAttr(Sema &S, OverloadCandidate *Cand) {
 }
 
 static void DiagnoseFailedExplicitSpec(Sema &S, OverloadCandidate *Cand) {
-  ExplicitSpecifier ES = ExplicitSpecifier::getFromDecl(Cand->Function);
+  assert(Cand->Function && "Candidate must be a function");
+  Function *CandFunc = Cand->Function;
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shafik wrote:

We use `Fn` elsewhere, we should be consistent throughout the file.

https://github.com/llvm/llvm-project/pull/98965