port_def: Add ignore for -Wextra-semi with Clang

Ignores warning: extra ';' inside a struct [-Wextra-semi] in generated proto files.

Amends #13492

src/google/protobuf/port_def.inc

@@ -1082,6 +1082,7 @@ static_assert(PROTOBUF_ABSL_MIN(20230125, 3),
 // for (int i = 0; i < file_->public_dependency_count(); ++i)
 //   for (int i = 0; i < public_dep->message_type_count(); ++i)
 #pragma clang diagnostic ignored "-Wshadow"
+#pragma clang diagnostic ignored "-Wextra-semi"
 #endif
 #ifdef __GNUC__
 #pragma GCC diagnostic push