[docs] Minor improvements in WiFi session page

[skip ci]

docs/user/wifi-sessions.rst

@@ -31,10 +31,7 @@ device's change admin under the "WiFi Sessions" tab.
 Scheduled Deletion of WiFi Sessions
 -----------------------------------
 
-OpenWISP Monitoring provides a celery task to automatically delete WiFi
-sessions older than a preconfigured number of days.
-
-.. note::
+.. important::
 
     If you have deployed OpenWISP using :doc:`ansible-openwisp2
     </ansible/index>` or :doc:`docker-openwisp </docker/index>`, then this
@@ -43,6 +40,9 @@ sessions older than a preconfigured number of days.
     This section is only for reference for users who wish to customize
     OpenWISP, or who have deployed OpenWISP in a different way.
 
+OpenWISP Monitoring provides a celery task to automatically delete WiFi
+sessions older than a preconfigured number of days.
+
 The celery task takes only one argument, i.e. number of days. You can
 provide any number of days in `args` key while configuring
 ``CELERY_BEAT_SCHEDULE`` setting.