Bug 1577316 - Omit principal from extension notification r=rpl

This was added in bug 1559697 , to show the Close button on macOS.
It had unwanted side effects, including the appearance of buttons
that don't have any apparent effect. To resolve this regression,
the change is undone.

Differential Revision: https://phabricator.services.mozilla.com/D49746

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

toolkit/components/extensions/parent/ext-notifications.js

@@ -44,7 +44,10 @@ function Notification(context, notificationsMap, id, options) {
       undefined,
       undefined,
       undefined,
-      context.principal, // ensures that Close button is shown on macOS.
+      // Principal is not set because doing so reveals buttons to control
+      // notification preferences, which are currently not implemented for
+      // notifications triggered via this extension API (bug 1589693).
+      undefined,
       context.incognito
     );
   } catch (e) {