[gnome-flashback] ci: don't run CI for tags

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 0e96f53f05f4c0ed0e80ecd451d80d32af440cdd
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Tue Mar 3 03:29:30 2020 +0200

    ci: don't run CI for tags

 .gitlab-ci.yml | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index f503552..6f35628 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -7,6 +7,8 @@ variables:
 build-ubuntu:
   image: ubuntu:devel
   stage: build
+  except:
+    - tags
   before_script:
     - apt-get update
     - apt-get install -q -y --no-install-recommends