Set monthly task to run by default

It was previously set to not run by default. Since the monthly task is
part of Figures normal workflow, we want it enabled by default. This can
be overridden by setting the ENV_VARS 'FIGURES' variable
`ENABLE_FIGURES_MONTHLY_METRICS` to False in the lms.env.json file

figures/settings/lms_production.py

@@ -49,7 +49,7 @@ def update_celerybeat_schedule(celerybeat_schedule_settings, figures_env_tokens)
                 ),
             }
 
-    if figures_env_tokens.get('ENABLE_FIGURES_MONTHLY_METRICS', False):
+    if figures_env_tokens.get('ENABLE_FIGURES_MONTHLY_METRICS', True):
         celerybeat_schedule_settings['figures-monthly-metrics'] = {
             'task': 'figures.tasks.run_figures_monthly_metrics',
             'schedule': crontab(0, 0, day_of_month=1),