Bug 1749598 p2 - Stop synchronizing the print_printer preference to content processes. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D150099

modules/libpref/Preferences.cpp

@@ -5815,6 +5815,7 @@ static const PrefListEntry sParentOnlyPrefBranchList[] = {
     PREF_LIST_ENTRY("identity.fxaccounts.account.device.name"),
     PREF_LIST_ENTRY("identity.fxaccounts.account.telemetry.sanitized_uid"),
     PREF_LIST_ENTRY("identity.fxaccounts.lastSignedInUserHash"),
+    PREF_LIST_ENTRY("print_printer"),
     PREF_LIST_ENTRY("services."),
 
     // Remove UUIDs