test: fix ratelimit test

the rate limiting logic slightly changed from redis-cell v0.2.2:
https://github.com/brandur/redis-cell/releases/tag/v0.2.2

tildes/tests/test_ratelimit.py

@@ -4,6 +4,7 @@
 from datetime import timedelta
 from itertools import permutations
 from random import randint
+from time import sleep
 
 from pytest import raises
 
@@ -153,6 +154,7 @@ def test_time_until_retry(redis):
     # first usage should be fine
     result = action.check_for_user_id(user_id)
     assert result.is_allowed
+    sleep(1.0)
 
     # second should fail, and require a wait of (period / limit) - 1 sec
     result = action.check_for_user_id(user_id)