[clang][sema] Sema::CheckFreeArguments - use cast<> instead of dyn_cast<> to avoid dereference of nullptr

The pointer is referenced immediately, so assert the cast is correct instead of returning nullptr

clang/lib/Sema/SemaChecking.cpp

@@ -11310,7 +11310,7 @@ void CheckFreeArgumentsCast(Sema &S, const std::string &CalleeName,
 /// Alerts the user that they are attempting to free a non-malloc'd object.
 void Sema::CheckFreeArguments(const CallExpr *E) {
   const std::string CalleeName =
-      dyn_cast<FunctionDecl>(E->getCalleeDecl())->getQualifiedNameAsString();
+      cast<FunctionDecl>(E->getCalleeDecl())->getQualifiedNameAsString();
 
   { // Prefer something that doesn't involve a cast to make things simpler.
     const Expr *Arg = E->getArg(0)->IgnoreParenCasts();