Update git submodules

* Update helpcontent2 from branch 'master'
  - Removed executable permission on image files
    
    Change-Id: I74aba60b5c77fe9acb6252c207846035a9f67473
    Reviewed-on: https://gerrit.libreoffice.org/66667
    Tested-by: Jenkins
Reviewed-by: Olivier Hallot <olivier.hallot@libreoffice.org>
    

helpcontent2 @ 5b3cb872

-Subproject commit f337457b70342b5dd28f9722c5e19f6ba7c47aaf
+Subproject commit 5b3cb872ff21a18460b76da364cf4f9130b8f285