Bug 1883673 - Remove majorRelease2022 Nimbus feature r=aminomancer,omc-reviewers,win-reviewers,gstoll,pbz,firefox-desktop-core-reviewers

This feature is no longer intended for experimentation and some of the things
it controls are no longer in product.

Differential Revision: https://phabricator.services.mozilla.com/D204514

browser/components/BrowserContentHandler.sys.mjs

@@ -322,12 +322,7 @@ function openBrowserWindow(
           Ci.nsILoadContext
         ).usePrivateBrowsing = true;
 
-        if (
-          AppConstants.platform == "win" &&
-          lazy.NimbusFeatures.majorRelease2022.getVariable(
-            "feltPrivacyWindowSeparation"
-          )
-        ) {
+        if (AppConstants.platform == "win") {
           lazy.WinTaskbar.setGroupIdForWindow(
             win,
             lazy.WinTaskbar.defaultPrivateGroupId