Increase Celery Chord Unlock Max Retries

In some cases, having multiple workers exhausts this limit quicker
than anticipated. The setting exists purely to protect against an
infinite loop, so having a slightly larger limit will not affect
performance.

src/mmw/mmw/settings/base.py

@@ -129,7 +129,7 @@ def get_env_setting(setting):
 CELERY_WORKER_DIRECT = True
 CELERY_CREATE_MISSING_QUEUES = True
 CELERY_CHORD_PROPAGATES = True
-CELERY_CHORD_UNLOCK_MAX_RETRIES = 20
+CELERY_CHORD_UNLOCK_MAX_RETRIES = 60
 # END CELERY CONFIGURATION