chore(aci): More frequent schedule_delayed_workflows (#102150)

We can switch to every 15s without negatively impacting existing
scheduling, but it'll make it possible for us to tweak US to actually
every 15 (rather than ever 20), allowing 4 per minute rather than 3.

Author: kcons

src/sentry/conf/server.py

@@ -951,7 +951,7 @@ def SOCIAL_AUTH_DEFAULT_USERNAME() -> str:
     },
     "flush-delayed-workflows": {
         "task": "workflow_engine:sentry.workflow_engine.tasks.workflows.schedule_delayed_workflows",
-        "schedule": timedelta(seconds=20),
+        "schedule": timedelta(seconds=15),
     },
     "sync-options": {
         "task": "options:sentry.tasks.options.sync_options",