frontend update to tabler beta 19 (#4029)

assets/sass/content.scss

@@ -5,6 +5,11 @@
  * file that was distributed with this source code.
  */
 
+/* used in security screens and other full-size pages */
+.page-center {
+    justify-content: center;
+}
+
 /* make sure that elements can be hidden without taking space (eg. hidden modals like the search or column visibility)  */
 .hidden-no-space {
     margin: 0;
@@ -33,11 +38,6 @@ td {
     }
 }
 
-.label-gray {
-    background-color: $gray-lte;
-    color: #666;
-}
-
 .open-edit {
     cursor: pointer;
 }