Bug 305818 - Document the removal of the Check Now buttons from Options-Advanced-Update. r=steffen

browser/locales/en-US/chrome/help/prefs.xhtml

@@ -472,9 +472,7 @@ Contributors:
       By default &brandShortName; automatically checks for updates to itself,
       to extensions and themes, and to search engines so you'll always know you
       have the most up-to-date version. You can turn off this behavior by
-      unchecking the appropriate checkbox here. You can also manually check for
-      updates to either &brandShortName; or your installed extensions and themes
-      by clicking the corresponding <em>Check Now...</em> button.</p>
+      unchecking the appropriate checkbox here.</p>
 
     <p><em>When updates to &brandShortName; are found,</em></p>