[gtksourceview] .gitlab-ci.yml: remove flatpak:image from config

[Christian Hergert <chergert src gnome org>]

commit 401e772ee8c8211d1614b6fa94b14bd54842f0e2
Author: Christian Hergert <chergert redhat com>
Date:   Thu Jul 28 01:39:38 2022 -0700

    .gitlab-ci.yml: remove flatpak:image from config
    
    As done elsewhere in other projects.

 .gitlab-ci.yml | 1 -
 1 file changed, 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b8fe93a6..c3d1f925 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -11,7 +11,6 @@ variables:
     FEDORA_IMAGE: "registry.gitlab.gnome.org/gnome/gtksourceview/fedora:latest"
 
 flatpak:
-    image: 'registry.gitlab.gnome.org/gnome/gnome-runtime-images/gnome:master'
     variables:
         BUNDLE: "gtksourceview-test-widget-dev.flatpak"
         MANIFEST_PATH: "org.gnome.GtkSourceView.TestWidget.json"