[gnome-todo/gbsneto/gtk4] ci: Use master image to build

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit f2eb7a343dda20d92789cda9b4a3cf034dbd13a7
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Wed Aug 1 10:59:21 2018 -0300

    ci: Use master image to build

 .gitlab-ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index f315826..c0e8e7b 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -59,7 +59,7 @@ ubuntu:devel:
 ##################
 
 flatpak:master:
-    image: registry.gitlab.gnome.org/gnome/gnome-runtime-images/gnome:3.28
+    image: registry.gitlab.gnome.org/gnome/gnome-runtime-images/gnome:master
     stage: flatpak
     variables:
       DEVELOPMENT_FLATPAK_ID: "TodoDevel"