Update git submodules

* Update helpcontent2 from branch 'libreoffice-7-0'
  to 6f9cff9a59d66c813d3947cdca65ff32c2d42821
  - Improve readabilty of SERIESSUM
    
    Change-Id: Ia5f4c2ccd335f9be8606bb192cc88d703d80d00c
    Reviewed-on: https://gerrit.libreoffice.org/c/help/+/95436
    Tested-by: Jenkins
    Reviewed-by: Olivier Hallot <olivier.hallot@libreoffice.org>
    (cherry picked from commit 67026c44ece5d04b41eb1c2f2c3ebf086d558bbd)
    Reviewed-on: https://gerrit.libreoffice.org/c/help/+/95740
    Reviewed-by: Ilmari Lauhakangas <ilmari.lauhakangas@libreoffice.org>
    
diff --git a/helpcontent2 b/helpcontent2
index 13eadf6..6f9cff9 160000
--- a/helpcontent2
+++ b/helpcontent2
@@ -1 +1 @@
Subproject commit 13eadf6de9cc483db44c399feb6a657fe8fde2a3
Subproject commit 6f9cff9a59d66c813d3947cdca65ff32c2d42821