Better, more consistent styling for plugin details Thickbox and TinyMCE help.

props avryl. fixes #26952.


git-svn-id: https://develop.svn.wordpress.org/trunk@27765 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/css/editor.css

@@ -73,6 +73,10 @@
 	width: calc( 100% - 36px );
 }
 
+.mce-wp-help .mce-window-head {
+	border-bottom: none;
+}
+
 .mce-textbox {
 	border: 1px solid #ddd;
 	-webkit-border-radius: 0;