Load autocomplete data when loading an issue page

This ensures the dropdown is fully available the moment a user starts
typing out a username, issue ID, etc. While this won't speed up loading
the autocomplete data itself it should at least make it less annoying
for the user.

app/assets/javascripts/gfm_auto_complete.js.coffee

@@ -68,7 +68,6 @@ GitLab.GfmAutoComplete =
             title:  sanitize(m.title)
             search: "#{m.iid} #{m.title}"
 
-    input.one 'focus', =>
     $.getJSON(@dataSource).done (data) ->
       # load members
       input.atwho 'load', '@', data.members