UI: Make BrowserDock native

After cleaning up the native flags in various places, and disabling
making sibling of native widgets native, BrowserDock was left in an
inconsistent state, since it requires being native for CEF to work
properly.

Make BrowserDock native.

UI/window-dock-browser.hpp

@@ -9,7 +9,7 @@ extern QCefCookieManager *panel_cookies;
 
 class BrowserDock : public OBSDock {
 public:
-	inline BrowserDock() : OBSDock() {}
+	inline BrowserDock() : OBSDock() { setAttribute(Qt::WA_NativeWindow); }
 
 	QScopedPointer<QCefWidget> cefWidget;