[pitivi] Non-fast-forward update to branch wip/piotrdrag/gtk-spelling

[Piotr Drąg <piotrdrag src gnome org>]

The branch 'wip/piotrdrag/gtk-spelling' 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:

  8c76c87... mainwindow: Correctly spell GTK+

Commits added to the branch:

  1ddd4c4... mainwindow: Correctly spell GTK+ in the about dialog