Remove unused protos::internal::{DeepCopy, DeepClone, GetOrPromoteExtension, GetUpbExtension, HasExtensionOrUnknown, MoveExtension}

PiperOrigin-RevId: 665934981

protos/protos.h

@@ -12,15 +12,9 @@ namespace protos {
 namespace internal {
 using hpb::internal::CreateMessage;
 using hpb::internal::CreateMessageProxy;
-using hpb::internal::DeepClone;
-using hpb::internal::DeepCopy;
 using hpb::internal::ExtensionIdentifier;
 using hpb::internal::GetArena;
 using hpb::internal::GetInternalMsg;
-using hpb::internal::GetOrPromoteExtension;
-using hpb::internal::GetUpbExtensions;
-using hpb::internal::HasExtensionOrUnknown;
-using hpb::internal::MoveExtension;
 using hpb::internal::PrivateAccess;
 using hpb::internal::Serialize;
 using hpb::internal::SetExtension;