Synapse: increase test delayed evt mgmt ratelimit

Targets config key added by element-hq/synapse#18019

Author: AndrewFerr

lib/SyTest/Homeserver/Synapse.pm

@@ -236,6 +236,11 @@ sub start
            },
         },
 
+        rc_delayed_event_mgmt => {
+            per_second => 1000,
+            burst_count => 1000,
+        }
+
         enable_registration => "true",
         enable_registration_without_verification => "true",
         databases => \%db_configs,