No need for custom tool button content item

After the fix provided by https://phabricator.kde.org/R242:cd8b6b71cebc27135a3864de7e12f13dd31cc9b1 there is no need for custom content item
1 job for master in 7 minutes and 8 seconds (queued for 25 minutes and 47 seconds)
Status Job ID Name Coverage
  Build
passed #14416
flatpak
flatpak

00:07:08