[gnome-todo] Remove the Git submodules

[Mathieu Bridon <mbridon src gnome org>]

commit 17c08d058ae4b4c4f59a417e178a2aa3d76caf0f
Author: Mathieu Bridon <bochecha daitauha fr>
Date:   Mon Oct 9 15:58:35 2017 +0200

    Remove the Git submodules
    
    It was partly removed in af76a496f832a8fe6236f5c6875736bf4d1e459b, but
    without removing this file Git would still think there was a submodule,
    which was making flatpak-builder fail.

 .gitmodules |    3 ---
 1 files changed, 0 insertions(+), 3 deletions(-)