Properly update retry_last_ts when hitting the maximum retry interval

This was broken in 1.90 when the maximum retry interval got changed from
almost infinite to a week (and made configurable).

fixes #16101

Signed-off-by: Nicolas Werner <nicolas.werner@hotmail.de>

synapse/storage/databases/main/transactions.py

@@ -257,7 +257,7 @@ def _set_destination_retry_timings_txn(
                 WHERE
                     EXCLUDED.retry_interval = 0
                     OR destinations.retry_interval IS NULL
-                    OR destinations.retry_interval < EXCLUDED.retry_interval
+                    OR destinations.retry_interval <= EXCLUDED.retry_interval
         """
 
         txn.execute(sql, (destination, failure_ts, retry_last_ts, retry_interval))