Fix leaking unclaimed incoming metadata

src/core/transport/chttp2/incoming_metadata.c

@@ -47,6 +47,10 @@ void grpc_chttp2_incoming_metadata_buffer_init(
 
 void grpc_chttp2_incoming_metadata_buffer_destroy(
     grpc_chttp2_incoming_metadata_buffer *buffer) {
+  size_t i;
+  for (i = 0; i < buffer->count; i++) {
+    grpc_mdelem_unref(buffer->elems[i].md);
+  }
   gpr_free(buffer->elems);
 }