feat(adminmanual): Create critical changes section for admins (26)

Signed-off-by: Anupam Kumar <kyteinsky@gmail.com>

Author: kyteinsky

admin_manual/release_notes/index.rst

@@ -14,7 +14,6 @@ These sub pages will cover the most important changes in Nextcloud, as well as s
 .. toctree::
    :maxdepth: 1
 
-   upgrade_to_27.rst
    upgrade_to_26.rst
 
 Changelog