Stop including registry_impl.h from registry_impl.h

PiperOrigin-RevId: 243615287
GitOrigin-RevId: c375a9322e98a03ccc1cb10a7f4c5d947969a154

cc/core/registry_impl.h

@@ -24,7 +24,6 @@
 #include "absl/strings/str_cat.h"
 #include "absl/synchronization/mutex.h"
 #include "tink/catalogue.h"
-#include "tink/core/registry_impl.h"
 #include "tink/key_manager.h"
 #include "tink/primitive_set.h"
 #include "tink/primitive_wrapper.h"