Update git submodules

* Update helpcontent2 from branch 'master'
  - tdf#117890 - Math Online Help: Remove unhelpful screenshots (2/2)
    
    removed EditSymbols.png and all subfolders
    
    Change-Id: Ie3fff059d02af0b76fd03ead64d1d33bf8056255
    Reviewed-on: https://gerrit.libreoffice.org/69128
    Tested-by: Jenkins
Reviewed-by: Olivier Hallot <olivier.hallot@libreoffice.org>
    

helpcontent2 @ 79599a40

-Subproject commit 34aca15b8c5711b2fce9c072364e04e3d11bcfc8
+Subproject commit 79599a40c6990b8649f88689d4761bbe6529388e