txg_sync should handle write errors in ZIL

The txg_sync thread will see certain buffers in a DR_IN_DMU_SYNC state
when ZIL is writing them out. Then it waits until the state changes, but
has an assertion to check that they were not DR_NOT_OVERRIDDEN. If the
data write failed with an error, ZIL will put it into the
DR_NOT_OVERRIDDEN state. It looks like the code will handle that state
without an issue, so we can just delete the assertion.

Sponsored-By: Wasabi Technology, Inc.
Signed-off-by: Richard Yao <richard.yao@klarasystems.com>

module/zfs/dbuf.c

@@ -4439,7 +4439,6 @@ dbuf_sync_leaf(dbuf_dirty_record_t *dr, dmu_tx_t *tx)
 	while (dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC) {
 		ASSERT(dn->dn_object != DMU_META_DNODE_OBJECT);
 		cv_wait(&db->db_changed, &db->db_mtx);
-		ASSERT(dr->dt.dl.dr_override_state != DR_NOT_OVERRIDDEN);
 	}
 
 	/*