fix(plugins/plugin-client-common): markdown expandable section left-border color not consistent

some issues with css priorities versus expanded sections

Author: starpit

plugins/plugin-client-common/web/scss/components/Terminal/_mixins.scss

@@ -577,7 +577,7 @@ $action-hover-delay: 210ms;
 }
 
 @mixin MarkdownTip {
-  .kui--markdown-tip {
+  div.kui--markdown-tip {
     @content;
   }
 }