Bug 1719939 - remove proton pref from static pref list and its last C++ consumer, r=mstange

Depends on D134311

Differential Revision: https://phabricator.services.mozilla.com/D134312

modules/libpref/init/StaticPrefList.yaml

@@ -1268,13 +1268,6 @@
   mirror: always
   rust: true
 
-# Enable Proton restyle. Requires restart.
-- name: browser.proton.enabled
-  type: RelaxedAtomicBool
-  value: true
-  mirror: always
-  rust: true
-
 - name: browser.proton.places-tooltip.enabled
   type: RelaxedAtomicBool
   value: false

widget/cocoa/NativeMenuSupport.mm

@@ -26,7 +26,7 @@ already_AddRefed<NativeMenu> NativeMenuSupport::CreateNativeContextMenu(dom::Ele
 }
 
 bool NativeMenuSupport::ShouldUseNativeContextMenus() {
-  return StaticPrefs::widget_macos_native_context_menus() && StaticPrefs::browser_proton_enabled();
+  return StaticPrefs::widget_macos_native_context_menus();
 }
 
 }  // namespace mozilla::widget