Update git submodules

* Update helpcontent2 from branch 'master'
  - Header and donation CSS tweaks
    
    Change-Id: I20e5610c08db700e12baffa9b62dcf8dfd0c4328
    Reviewed-on: https://gerrit.libreoffice.org/69278Reviewed-by: Olivier Hallot <olivier.hallot@libreoffice.org>
Tested-by: Olivier Hallot <olivier.hallot@libreoffice.org>
    Tested-by: Jenkins
    

helpcontent2 @ 34aca15b

-Subproject commit e6dfe7b36ebfda217fe89c18b656d2eee72c18ce
+Subproject commit 34aca15b8c5711b2fce9c072364e04e3d11bcfc8