docs: replace removed updateAttributesInterval with current sync behavior

The updateAttributesInterval occ config key was removed in NC20 via
the RemoveRefreshTime migration (nextcloud/server#22583). The background
sync interval is now auto-calculated in Jobs/Sync.php based on the number
of mapped users and the minimum paging size, clamped to 30 min–12 h,
targeting one full sync per day.

Replace the stale "Attribute update interval" section (which still
referenced the removed occ command) with an accurate description of
the current auto-calculated behavior.

Fixes #11088

Signed-off-by: John Molakvoæ (skjnldsv) <skjnldsv@protonmail.com>

Author: skjnldsv

admin_manual/configuration_user/user_auth_ldap.rst

@@ -645,26 +645,17 @@ Additional configuration options via occ
 
 Few configuration settings can only be set on command line via ``occ``.
 
-Attribute update interval
-^^^^^^^^^^^^^^^^^^^^^^^^^
+Background sync interval
+^^^^^^^^^^^^^^^^^^^^^^^^
 
-The LDAP backend will update user information that is used within Nextcloud
-with the values provided by the LDAP server. For instance these are email,
-quota or the avatar. This happens on every login, the first detection of a user
-from LDAP and regularly by a background job.
+The LDAP backend updates user attributes (email, quota, avatar, and others) on
+every login, on first detection of a new user, and periodically via a background
+job.
 
-The interval value determines the time between updates of the values and is
-used to avoid frequent overhead, including time-expensive write actions to
-the database.
-
-The interval is described in seconds and it defaults to 86400 equalling a day.
-It is not a per-configuration option.
-
-The value can be modified by::
-
-  sudo -E -u www-data php occ config:app:set user_ldap updateAttributesInterval --value=86400
-
-A value of 0 will update it on every of the named occasions.
+The background job recalculates its run interval after each cycle. The goal is
+to process every known LDAP user approximately once per day. The interval is
+derived from the total number of mapped users and the smallest configured LDAP
+paging size, then clamped to a minimum of 30 minutes and a maximum of 12 hours.
 
 Administrative Group mapping
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^