Remove sleep by Azat suggestion,...

Remove sleep by Azat suggestion, https://github.com/ClickHouse/ClickHouse/pull/8288#pullrequestreview-336615781

dbms/tests/integration/test_dictionary_ddl_on_cluster/test.py

@@ -61,7 +61,6 @@ def test_dictionary_ddl_on_cluster(started_cluster):
         node.query("ALTER TABLE sometbl UPDATE value = 'new_key' WHERE 1")
 
     ch1.query("SYSTEM RELOAD DICTIONARY ON CLUSTER 'cluster' `default.somedict`")
-    time.sleep(2)  # SYSTEM RELOAD DICTIONARY is an asynchronous query
 
     for num, node in enumerate([ch1, ch2, ch3, ch4]):
         assert node.query("SELECT dictGetString('default.somedict', 'value', toUInt64({}))".format(num)) == 'new_key' + '\n'