Revert "Make private browsing asserts more useful"

This reverts commit b09a1385f5.

qutebrowser/browser/commands.py

@@ -124,7 +124,7 @@ class CommandDispatcher:
             private = self._tabbed_browser.is_private
 
         if window or private:
-            assert isinstance(private, bool), private
+            assert isinstance(private, bool)
             tabbed_browser = self._new_tabbed_browser(private)
             tabbed_browser.tabopen(url)
             tabbed_browser.window().show()

qutebrowser/mainwindow/mainwindow.py

@@ -224,7 +224,6 @@ class MainWindow(QWidget):
             model=self._download_model)
 
         self.is_private = config.val.content.private_browsing or private
-        assert isinstance(self.is_private, bool), private
 
         self.tabbed_browser: tabbedbrowser.TabbedBrowser = tabbedbrowser.TabbedBrowser(
             win_id=self.win_id, private=self.is_private, parent=self)