Remove unused headers.

PiperOrigin-RevId: 588439704
diff --git a/src/google/protobuf/repeated_ptr_field.cc b/src/google/protobuf/repeated_ptr_field.cc
index 1cc6bbe..49c29fe 100644
--- a/src/google/protobuf/repeated_ptr_field.cc
+++ b/src/google/protobuf/repeated_ptr_field.cc
@@ -19,7 +19,6 @@
 #include "absl/base/prefetch.h"
 #include "absl/log/absl_check.h"
 #include "google/protobuf/arena.h"
-#include "google/protobuf/implicit_weak_message.h"
 #include "google/protobuf/message_lite.h"
 #include "google/protobuf/port.h"
 #include "google/protobuf/repeated_field.h"