[evince] ci: Run flatpak CI only for master

[Germán Poo-Caamaño <gpoo src gnome org>]

commit 60f2692035f5ec008d875ef9b708fb0c447cb13a
Author: Germán Poo-Caamaño <gpoo gnome org>
Date:   Wed Oct 3 23:31:53 2018 -0300

    ci: Run flatpak CI only for master
    
    The current flatpak scripts runs the job using the manifest,
    which retrieves and builds the source from git master. Therefore,
    it is unhelpful to build the MR.
    
    For the moment, we will build the flatpak module only for
    commits on master. Once we fix the script, we can extend the
    CI tests to run for MR as well.

 .gitlab-ci.yml | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index ccc11fb5..34e78dd5 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -63,6 +63,9 @@ gtk-doc:
 flatpak:
     image: registry.gitlab.gnome.org/gnome/gnome-runtime-images/gnome:master
     stage: build
+    only:
+        refs:
+            - master
 
     before_script:
         - dnf install -y flatpak-builder flatpak