Core: Remove assert about non-Main tag for embedded collections.

Given current tag/flag handling situation (see also #88555 and #90610),
it is not yet possible to ensure matching tags between embedded data and
their owner ID. Furthermore, a non-main Scene should also tag its master
collection as non-main, so current test was not correct anyway.

source/blender/blenkernel/intern/collection.cc

@@ -238,7 +238,6 @@ static ID **collection_owner_pointer_get(ID *id)
   if ((id->flag & LIB_EMBEDDED_DATA) == 0) {
     return nullptr;
   }
-  BLI_assert((id->tag & LIB_TAG_NO_MAIN) == 0);
 
   Collection *master_collection = (Collection *)id;
   BLI_assert((master_collection->flag & COLLECTION_IS_MASTER) != 0);