chore: add removal of OCA.Sharing.ExternalLinkActions

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

Author: susnux

developer_manual/app_publishing_maintenance/app_upgrade_guide/upgrade_to_33.rst

@@ -26,6 +26,8 @@ Removed APIs
 - The global ``md5`` implementation is removed. It was deprecated since Nextcloud 20 and not used by Nextcloud anymore.
   If you still need a ``md5`` implementation you can just use some external package like `crypto-browserify <https://www.npmjs.com/package/crypto-browserify>`_.
 - The ``OC.SystemTags`` api was removed. If you need to get the list of system tags, check `this merge request <https://github.com/nextcloud/files_retention/pull/855>`_ for how to fetch the tags directly.
+- The `OCA.Sharing.ExternalLinkActions` API was deprecated in Nextcloud 23 and is now removed.
+  It was replaced with `OCA.Sharing.ExternalShareAction` which now have a proper API by using `registerSidebarAction` from `@nextcloud/sharing` instead.
 
 Back-end changes
 ----------------