[gtk] (2 commits) Non-fast-forward update to branch wip/smcv/aboutdialog-licenses

[Simon McVittie <smcv src gnome org>]

The branch 'wip/smcv/aboutdialog-licenses' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  6d8fb83... aboutdialog: Update precondition checks for new licenses ad
  b7136d1... aboutdialog: Document the new licenses added in 3.24.20

Commits added to the branch:

  177aeca... aboutdialog: Update precondition checks for new licenses ad
  4db3f14... aboutdialog: Document the new licenses added in 3.24.20