Bug 1911887 - Enable langpack update staging when Thunderbird updates. r=mkmelin

Differential Revision: https://phabricator.services.mozilla.com/D219697

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

mail/app/profile/all-thunderbird.js

@@ -123,6 +123,8 @@ pref("app.update.service.enabled", true);
 pref("app.update.BITS.enabled", false);
 #endif
 
+pref("app.update.langpack.enabled", true);
+
 // Release notes URL
 pref("app.releaseNotesURL", "https://live.thunderbird.net/%APP%/releasenotes?locale=%LOCALE%&version=%VERSION%&channel=%CHANNEL%&os=%OS%&buildid=%APPBUILDID%");