Bug 1666252 - Margin adjustment for WNPanel r=andreio

Differential Revision: https://phabricator.services.mozilla.com/D95421

browser/themes/shared/customizableui/panelUI.inc.css

@@ -1989,7 +1989,7 @@ panelview:not([mainview]) #PanelUI-whatsNew-title {
 
 #PanelUI-whatsNew .whatsNew-message-body {
   padding: 5px 0 10px;
-  margin: 0 16px;
+  margin: 10px 16px;
   text-align: inherit;
   text-decoration: none;
   color: inherit;