Remove redundant check for default collation.

The operative check is for a deterministic collation, so the check for
DEFAULT_COLLATION is redundant. Furthermore, it will be wrong if we
ever support a non-deterministic default collation.

Author: Andreas Karlsson
Discussion: https://postgr.es/m/60929555-4709-40a7-b136-bcb44cff5a3c@proxel.se

src/backend/utils/adt/varlena.c

@@ -2540,7 +2540,6 @@ btvarstrequalimage(PG_FUNCTION_ARGS)
 	locale = pg_newlocale_from_collation(collid);
 
 	if (locale->collate_is_c ||
-		collid == DEFAULT_COLLATION_OID ||
 		pg_locale_deterministic(locale))
 		PG_RETURN_BOOL(true);
 	else