Temp fix, since update check is an extension, and extensions can't
currently modify notebookbars.

This needs implementation of something like
https://wiki.openoffice.org/wiki/Framework/Article/Addon_Menu_Toolbar_Merging
for notebookbar popup menus. Such that Addons.xcs provide some merge
points with notebookbar menu IDs, we can then plug into existing popup
menus.

Change-Id: If30525fec1e7be0429e351588614618c5f56cdd4
Reviewed-on: https://gerrit.libreoffice.org/69735Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
Tested-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
(cherry picked from commit 98174e16)
Reviewed-on: https://gerrit.libreoffice.org/69741Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>
Tested-by: Katarina Behrens <Katarina.Behrens@cib.de>