Bug 1573103 - Can not show all characters on About Nightly window. r=dao

Add a width to the wordmark background-image

Differential Revision: https://phabricator.services.mozilla.com/D42740

--HG--
extra : moz-landing-system : lando

browser/base/content/aboutDialog.css

@@ -14,6 +14,7 @@
 #rightBox {
   background-image: url("chrome://branding/content/about-wordmark.svg");
   background-repeat: no-repeat;
+  background-size: 288px auto;
   /* padding-top creates room for the wordmark */
   padding-top: 38px;
   margin-top:20px;