MDEV-27234 fixup: Remove a bogus assertion

Starting with commit 8f8ba758
the assertion would fail in
./mtr --mysqld=--innodb-adaptive-hash-index innodb.instant_alter_crash
and it would keep failing even after
commit d2e649ae

storage/innobase/btr/btr0cur.cc

@@ -2393,9 +2393,8 @@ dberr_t btr_cur_search_to_nth_level(dict_index_t *index, ulint level,
 		page hash index, while holding search latch. */
 		if (!btr_search_enabled) {
 		} else if (tuple->info_bits & REC_INFO_MIN_REC_FLAG) {
-			ut_ad(index->is_instant());
 			/* This may be a search tuple for
-			btr_pcur_restore_position(). */
+			btr_pcur_t::restore_position(). */
 			ut_ad(tuple->is_metadata()
 			      || (tuple->is_metadata(tuple->info_bits
 						     ^ REC_STATUS_INSTANT)));