Fix the Perma failure for navigation-id-initial-load.tentative.html

Differential Revision: https://phabricator.services.mozilla.com/D192690

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1862907
gecko-commit: 237a99d085dd3d8129d27f9416fc606fe102079b
gecko-reviewers: emilio
diff --git a/performance-timeline/navigation-id-initial-load.tentative.html b/performance-timeline/navigation-id-initial-load.tentative.html
index 93ddcff..b996f0f 100644
--- a/performance-timeline/navigation-id-initial-load.tentative.html
+++ b/performance-timeline/navigation-id-initial-load.tentative.html
@@ -28,7 +28,7 @@
       // Assert navigation id exists in a NavigationTiming entry.
       const navigationIdOfNavigationTiming =
         performance.getEntriesByType('navigation')[0].navigationId;
-      assert_not_equals(navigationIdOfNavigationTiming, null,
+      assert_true(!!navigationIdOfNavigationTiming,
         'Navigation Id of a navigation timing entry should exist at initial navigation');
 
       // Assert navigation id exists in PaintTiming entries and are all the same.