Bug 1575088 - Fix the style issue of the permission granted indicator. r=johannh

This patch fixes the style issue by make the container of the permission
granted indicator to centered align its children.

Differential Revision: https://phabricator.services.mozilla.com/D42617

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

browser/components/controlcenter/content/identityPanel.inc.xul

@@ -65,7 +65,7 @@
             when-connection="not-secure secure secure-ev secure-cert-user-overridden file extension">
         <vbox id="identity-popup-permissions-content" flex="1" role="group"
               aria-labelledby="identity-popup-permissions-headline">
-          <hbox>
+          <hbox align="center">
             <label id="identity-popup-permissions-headline"
                    value="&identity.permissions2;"/>
             <image id="identity-popup-permissions-granted-indicator"/>