remove incorrect and unnecessary margin declaration. b=284762 r=kmgerich

browser/themes/pinstripe/browser/preferences/preferences.css

@@ -118,7 +118,6 @@ radio[pane=paneAdvanced] {
   background-color: transparent;
   border: none;
   padding: 1px 0px 0px 0px;
-  margin: none;
 }
 
 prefpane button {