Bug 1304180 - Set taskcluster artifact expiration to 28 days on try r=dustin

MozReview-Commit-ID: ECXCs9EkOYI

--HG--
extra : rebase_source : e1c52eaa1c3324b44851f9d3c88d69d0174b0f21

taskcluster/taskgraph/transforms/task.py

@@ -518,7 +518,7 @@ def build_task(config, tasks):
             ])
 
         if 'expires-after' not in task:
-            task['expires-after'] = '14 days' if config.params['project'] == 'try' else '1 year'
+            task['expires-after'] = '28 days' if config.params['project'] == 'try' else '1 year'
 
         if 'deadline-after' not in task:
             task['deadline-after'] = '1 day'