Push event: Nest link in strong tag, not vice-versa

Closes #1022

app/views/events/event/_push.html.haml

@@ -4,8 +4,8 @@
   - if event.rm_ref?
     %strong= event.ref_name
   - else
-    = link_to namespace_project_commits_path(event.project.namespace, event.project, event.ref_name) do
-      %strong= event.ref_name
+    %strong
+      = link_to event.ref_name, namespace_project_commits_path(event.project.namespace, event.project, event.ref_name)
   at
   = link_to_project event.project