Fix #15885 - Removed back labels from Metro login form

Pull-request: #15894
Fixes: #15885

Signed-off-by: William Desportes <williamdes@wdes.fr>

themes/metro/scss/_common.scss

@@ -19,6 +19,10 @@ body#loginform {
   margin: 0;
   background-color: #666;
 
+  form#login_form label {
+    display: none !important;
+  }
+
   #page_content {
     background-color: $navi-background;
     margin: 0 !important;
@@ -140,10 +144,6 @@ body#loginform {
   }
 }
 
-form.login label {
-  display: none;
-}
-
 .turnOffSelect {
   -moz-user-select: none;
   -khtml-user-select: none;