NFC: silence some -Wrange-loop-analysis warnings. (#32634)

Author: dan-zheng

lib/AST/ASTDumper.cpp

@@ -3524,7 +3524,7 @@ namespace {
       if (T->getParent())
         printRec("parent", T->getParent());
 
-      for (const auto arg : T->getDirectGenericArgs())
+      for (const auto &arg : T->getDirectGenericArgs())
         printRec(arg);
       PrintWithColorRAII(OS, ParenthesisColor) << ')';
     }

lib/AST/TypeWalker.cpp

@@ -39,7 +39,7 @@ class Traversal : public TypeVisitor<Traversal, bool>
     if (auto parent = ty->getParent())
       if (doIt(parent)) return true;
 
-    for (const auto arg : ty->getDirectGenericArgs())
+    for (const auto &arg : ty->getDirectGenericArgs())
       if (doIt(arg))
         return true;