read propper env vars for scheduled tasks

shiftregister/settings.py

@@ -156,11 +156,11 @@ CELERY_BEAT_SCHEDULE = {
     },
     "send-messages-every-120-seconds": {
         "task": "shiftregister.app.tasks.send_messages",
-        "schedule": float(getenv("SHIFT_IMPORT_INTERVAL", 120.0)),  # seconds
+        "schedule": float(getenv("MESSAGE_SEND_INTERVAL", 120.0)),  # seconds
     },
     "send-reminders-every-300-seconds": {
         "task": "shiftregister.app.tasks.send_reminders",
-        "schedule": float(getenv("SHIFT_IMPORT_INTERVAL", 300.0)),  # seconds
+        "schedule": float(getenv("REMINDER_SEND_INTERVAL", 300.0)),  # seconds
     },
 }