Update git submodules

* Update helpcontent2 from branch 'master'
  - tdf#68103 Mark differences between Draw and Impress
    
    Although the 2 modules share a common kernel, the nomeclature,
    menus and master pages/slides are different.
    
    Change-Id: Id4282b2ebaf48a57b753ff0cefa228c3f3bdc644
    Reviewed-on: https://gerrit.libreoffice.org/73578
    Tested-by: Jenkins
Reviewed-by: Olivier Hallot <olivier.hallot@libreoffice.org>
    

helpcontent2 @ 2c84c28b

-Subproject commit 2eb1257145949b53d085edf37d7c599bf17f0051
+Subproject commit 2c84c28bc30456c8eb4e0473887ce1d5ff3e4209