Update git submodules

* Update helpcontent2 from branch 'master'
  - Let's have Content-Type everywhere.
    
    Change-Id: I000658561d76d6a95a4acbc621db5e3f6d081e08
    Reviewed-on: https://gerrit.libreoffice.org/59051
    Tested-by: Jenkins
Reviewed-by: Jan Holesovsky <kendy@collabora.com>
    

helpcontent2 @ 5ccfc30b

-Subproject commit 8d728edf4a9bbf066c3173a0349798d9465bad61
+Subproject commit 5ccfc30b13663a52686cd040cb574bc0c0dc652c