Remove snippet expiration date from UI

app/views/projects/snippets/_snippet.html.haml

@@ -5,13 +5,6 @@
     %span.cgray.monospace.tiny.pull-right
       = snippet.file_name
 
-  %small.pull-right.cgray
-    Expires:
-    - if snippet.expires_at
-      = snippet.expires_at.to_date.to_s(:short)
-    - else
-      Never
-
   .snippet-info
     = "##{snippet.id}"
     %span