AC-2039 Remove unnecessary Contex Menu plugin to avoid deprecation notice

Author: karyna-t

app/code/Magento/Backend/view/adminhtml/templates/widget/form/element.phtml

@@ -94,7 +94,7 @@ $htmlId = $element->getHtmlId();
                 theme : "advanced",
                 elements : "{$block->escapeJs($element->getName())}",
                 plugins : "inlinepopups,style,layer,table,save,advhr,advimage,advlink,emotions,iespell,"
-                    + "insertdatetime,preview,zoom,media,searchreplace,print,contextmenu,paste,directionality,"
+                    + "insertdatetime,preview,zoom,media,searchreplace,print,paste,directionality,"
                     + "fullscreen,noneditable,visualchars,nonbreaking,xhtmlxtras",
                 theme_advanced_buttons1 : "newdocument,|,bold,italic,underline,strikethrough,|"
                     + ",justifyleft,justifycenter,justifyright,justifyfull,|"

app/code/Magento/Cms/Model/Wysiwyg/DefaultConfigProvider.php

@@ -46,7 +46,6 @@ public function getConfig(\Magento\Framework\DataObject $config) : \Magento\Fram
                         'media',
                         'noneditable',
                         'table',
-                        'contextmenu',
                         'paste',
                         'code',
                         'help',