[AIRFLOW-1698] Remove SCHEDULER_RUNS env var in systemd

In the very early days, the Airflow scheduler
needed to be restarted
every so often to take new DAG_FOLDERS mutations
into account properly. This is no longer
required.

Closes #2677 from mistercrunch/scheduler_runs

scripts/systemd/airflow

@@ -16,6 +16,4 @@
 #
 # AIRFLOW_CONFIG=
 # AIRFLOW_HOME=
-#
-# required setting, 0 sets it to unlimited. Scheduler will get restart after every X runs
-SCHEDULER_RUNS=5
+

scripts/systemd/airflow-scheduler.service

@@ -21,9 +21,9 @@ EnvironmentFile=/etc/sysconfig/airflow
 User=airflow
 Group=airflow
 Type=simple
-ExecStart=/bin/airflow scheduler -n ${SCHEDULER_RUNS}
+ExecStart=/bin/airflow scheduler
 Restart=always
 RestartSec=5s
 
 [Install]
-WantedBy=multi-user.target
+WantedBy=multi-user.target