Bug 1787243 - Fix dead w3schools color names link. r=me

suite/locales/en-US/chrome/common/help/composer_help.xhtml

@@ -419,7 +419,7 @@
         supported color names
         <a href="http://www.w3.org/TR/CSS21/syndata.html#color-units">here</a>,
         and another list of commonly supported color names 
-        <a href="http://www.w3schools.com/html/html_colornames.asp">here</a>.
+        <a href="https://www.w3schools.com/colors/colors_names.asp">here</a>.
       </li>
     </ul>
   </li>