Added GitLab restart required help block to session_expire_seconds

app/views/admin/application_settings/_form.html.haml

@@ -87,6 +87,7 @@
       = f.label :session_expire_seconds, 'Session duration (seconds)', class: 'control-label col-sm-2'
       .col-sm-10
         = f.number_field :session_expire_seconds, class: 'form-control'
+        %span.help-block#session_expire_seconds_help_block GitLab restart is required to apply changes        
     .form-group
       = f.label :restricted_signup_domains, 'Restricted domains for sign-ups', class: 'control-label col-sm-2'
       .col-sm-10
@@ -101,4 +102,4 @@
             Allow users to register any application to use GitLab as an OAuth provider
   .form-actions
-    = f.submit 'Save', class: 'btn btn-primary'
+    = f.submit 'Save', class: 'btn btn-primary'
\ No newline at end of file