Update git submodules

* Update helpcontent2 from branch 'master'
  - Donation button and sticky header for Help
    
    Task: https://redmine.documentfoundation.org/issues/2815
    
    Header was made sticky on non-mobile by using position: sticky.
    This was the only way to make it work with the grid without
    carving magic numbers into stone. IE11 ignores it, but so what?
    
    Donation text was made shorter.
    
    The Google search and the donation button were wrapped in a
    container to make it easy to haul them all over the place.
    
    Lots of tweaks were made to the grid areas and the styles of
    the bottom elements to make everything fit nicely in the new
    markup order. The result was tested on IE11 to make sure it
    degrades gracefully.
    
    The Displayarea element had a fixed width (my old mistake),
    which made the min-width: 960px layout look very uncool.
    
    Change-Id: I131a1e82290bc3381c938acb4dc9dbc408fb2ba7
    Reviewed-on: https://gerrit.libreoffice.org/68890
    Tested-by: Jenkins
Reviewed-by: Olivier Hallot <olivier.hallot@libreoffice.org>
Tested-by: Olivier Hallot <olivier.hallot@libreoffice.org>
    

helpcontent2 @ eb2972e0

-Subproject commit 0d749e887dc08a756215296e531650e97544aa92
+Subproject commit eb2972e06b1ac3210f1de1a6e9ade2d049aaf976