styling: removing unused td-gravatar class

rhodecode/public/css/tables.less

@@ -123,11 +123,6 b' table.dataTable {'
             }
         }
 
-        &.td-gravatar {
-            width: 16px;
-            padding: 0 5px;
-        }
-
         &.tags-col {
             padding-right: 0;
         }