mgr/dashboard: Update release notes and doc

-  for removal of old dashoard support

Signed-off-by: Afreen Misbah <[email protected]>

Author: afreen23

PendingReleaseNotes

@@ -194,6 +194,10 @@
   C `rbd_mirror_image_resync()`, and Python `Image.mirror_image_resync()` --
   will return EINVAL instead of ENOENT when mirroring is not enabled.
 
+* DASHBOARD: Removed the older landing page which was deprecated in quincy.
+  The admin can no longer enable the older, deprecated landing page layout by 
+  adjusting FEATURE_TOGGLE_DASHBOARD.
+
 >=19.2.1
 
 * CephFS: The `fs subvolume create` command now allows tagging subvolumes through option

doc/mgr/dashboard.rst

@@ -129,16 +129,6 @@ updates on any changes in the cluster and allows quick access to other sections
 
 .. image:: dashboard-landing-page.png
 
-
-.. note::
-  You can change the landing page to the previous version from:
-  ``Cluster >> Manager Modules >> Dashboard >> Edit``.
-  Editing the ``FEATURE_TOGGLE_DASHBOARD`` option will change the landing page, from one view to another.
-
-  Note that the previous version of the landing page will be disabled in future releases.
-
-.. _dashboard-landing-page-details:
-
 Details
 """""""
 Provides an overview of the cluster configuration, displaying various critical aspects of the cluster.