Update git submodules

* Update helpcontent2 from branch 'master'
  - it is not possible to set negative angle for watermark
    
    Change-Id: Ie51a36a95c8443d56a559bf79fb9a674e9e1a283
    Reviewed-on: https://gerrit.libreoffice.org/59615
    Tested-by: Jenkins
Reviewed-by: Olivier Hallot <olivier.hallot@libreoffice.org>
    

helpcontent2 @ 2c50cc22

-Subproject commit f3124329e336603ba6684e913a61a58e7a202020
+Subproject commit 2c50cc225fe75ff659eda9b52f70ac139054cdbc