Delete dead Message::GetInvariantPerBuild

This is a protected member function and not part of the public interface.

PiperOrigin-RevId: 562774514

src/google/protobuf/message.cc

@@ -212,10 +212,6 @@ size_t Message::SpaceUsedLong() const {
   return GetReflection()->SpaceUsedLong(*this);
 }
 
-uint64_t Message::GetInvariantPerBuild(uint64_t salt) {
-  return salt;
-}
-
 namespace internal {
 void* CreateSplitMessageGeneric(Arena* arena, const void* default_split,
                                 size_t size, const void* message,

src/google/protobuf/message.h

@@ -411,9 +411,6 @@ class PROTOBUF_EXPORT Message : public MessageLite {
   size_t MaybeComputeUnknownFieldsSize(size_t total_size,
                                        internal::CachedSize* cached_size) const;
 
-
- protected:
-  static uint64_t GetInvariantPerBuild(uint64_t salt);
 };
 
 namespace internal {