[Clang][NFC] Remove unnecessary copy (llvm#100688)

Reported by Static Analyzer Tool:

In Sema::checkIncorrectVTablePointerAuthenticationAttribute(): Using the
auto keyword without an & causes the copy of an object of type
CXXBaseSpecifier.

Author: smanna12

clang/lib/Sema/SemaDeclCXX.cpp

@@ -10385,7 +10385,7 @@ void Sema::checkIncorrectVTablePointerAuthenticationAttribute(
   while (1) {
     assert(PrimaryBase);
     const CXXRecordDecl *Base = nullptr;
-    for (auto BasePtr : PrimaryBase->bases()) {
+    for (const CXXBaseSpecifier &BasePtr : PrimaryBase->bases()) {
       if (!BasePtr.getType()->getAsCXXRecordDecl()->isDynamicClass())
         continue;
       Base = BasePtr.getType()->getAsCXXRecordDecl();