Remove unused internal function from the public section of Map.

PiperOrigin-RevId: 805973468

Author: sbenzaquen

src/google/protobuf/map.h

@@ -1421,7 +1421,7 @@ class Map : private internal::KeyMapBase<internal::KeyForBase<Key>> {
 
   void swap(Map& other) {
     if (arena() == other.arena()) {
-      InternalSwap(&other);
+      this->InternalSwap(&other);
     } else {
       size_t other_size = other.size();
       Node* other_copy = this->CloneFromOther(other);
@@ -1433,10 +1433,6 @@ class Map : private internal::KeyMapBase<internal::KeyForBase<Key>> {
     }
   }
 
-  void InternalSwap(Map* other) {
-    internal::UntypedMapBase::InternalSwap(other);
-  }
-
   hasher hash_function() const { return {}; }
 
   size_t SpaceUsedExcludingSelfLong() const {