MC-3406: Explicit Background Attributes for Tab

 - fix static failures

Author: cspruiell

app/code/Magento/PageBuilder/Model/Stage/Config.php

@@ -85,6 +85,8 @@ class Config
      * @param \Magento\PageBuilder\Model\Wysiwyg\InlineEditingSupportedAdapterList $inlineEditingChecker
      * @param \Magento\PageBuilder\Model\WidgetInitializerConfig $widgetInitializerConfig
      * @param array $data
+     *
+     * @SuppressWarnings(PHPMD.ExcessiveParameterList)
      */
     public function __construct(
         \Magento\PageBuilder\Model\ConfigInterface $config,

app/code/Magento/PageBuilder/view/adminhtml/web/css/source/content-type/slider/_default.less

@@ -339,7 +339,7 @@
             width: 14px;
             button {
                 background: transparent;
-                border: 1px solid #ccc;
+                border: 1px solid @color-gray;
                 border-radius: 10px;
                 box-shadow: none;
                 cursor: pointer;