MAGETWO-90441: Allow inline editing of Heading from stage

- fix static less rules

Author: anthoula

app/code/Magento/PageBuilder/view/adminhtml/web/css/source/_module.less

@@ -10,9 +10,9 @@
 @import '_buttons.less';
 //  Import Slick
 @import 'slick/_slick.less';
-//  Import Panel {less}
+//  Import Panel
 @import '_panel.less';
-//  Import Page-builder {less}
+//  Import Page-builder
 @import '_page-builder.less';
 //  Import Image Uploader UI component
 @import 'form/element/_import.less';

app/code/Magento/PageBuilder/view/adminhtml/web/css/source/_toolbar.less

@@ -34,7 +34,7 @@
     -o-transition: opacity 200ms, top 200ms, visibility 200ms;
     -webkit-transition: opacity 200ms, top 200ms, visibility 200ms;
     background-color: @color-gray94;
-    border: 1px solid #c0c0c0;
+    border: 1px solid @color-gray75;
     height: 38px;
     left: -2px;
     opacity: 0;