Bug 1724300 - Remove What's New Panel, ToolbarPanelHub components & related tests & references r=desktop-theme-reviewers,omc-reviewers,aminomancer,pdahiya,emilio,devtools-reviewers,firefox-desktop-core-reviewers ,home-newtab-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D201867

browser/components/asrouter/modules/ASRouterTargeting.sys.mjs

@@ -72,12 +72,6 @@ XPCOMUtils.defineLazyPreferenceGetter(
   "browser.newtabpage.activity-stream.asrouter.userprefs.cfr.addons",
   true
 );
-XPCOMUtils.defineLazyPreferenceGetter(
-  lazy,
-  "isWhatsNewPanelEnabled",
-  "browser.messaging-system.whatsNewPanel.enabled",
-  false
-);
 XPCOMUtils.defineLazyPreferenceGetter(
   lazy,
   "hasAccessedFxAPanel",
@@ -704,9 +698,6 @@ const TargetingGetters = {
   get hasAccessedFxAPanel() {
     return lazy.hasAccessedFxAPanel;
   },
-  get isWhatsNewPanelEnabled() {
-    return lazy.isWhatsNewPanelEnabled;
-  },
   get userPrefs() {
     return {
       cfrFeatures: lazy.cfrFeaturesUserPref,