Update git submodules

* Update helpcontent2 from branch 'master'
  - Create XSLT replacement table for missing icons
    
    Missing UI icons have a replacement table in
    /core/icon-themes/colibre/links.txt
    
    Help must also use this replacement table when Help
    pages have missing icons. The previous approach was a manual
    creation of a XSLT for the replacement.
    
    The patch moves the replacement table creation inside the
    Custom makefile, making it automatic and carrying changes
    of the original links.txt source.
    
    Change-Id: I7f834fa03bbd85f329efbec43e5c51cc86d51586
    Reviewed-on: https://gerrit.libreoffice.org/70080
    Tested-by: Jenkins
Reviewed-by: Olivier Hallot <olivier.hallot@libreoffice.org>
    

helpcontent2 @ 61f44912

-Subproject commit 0e323bedb182d71c72ef08ec0f745bb60830a2c3
+Subproject commit 61f44912beec99f6211399ce567274aa369f817d