flatpak: Use libhandy-0-0 branch instead of master
The master branch points to the next libhandy release that will be 1.0 so using master breaks the build.
This patch uses the current stable release instead to try to use master.
The master branch points to the next libhandy release that will be 1.0 so using master breaks the build.
This patch uses the current stable release instead to try to use master.