pythongh-157170: Restore use_env() after test_use_prescr_screen in test_curses (pythonGH-157171)

curses.use_env() sets a process-wide ncurses setting, not a property of
the screen it is called on.

Author: iamsharduld

Lib/test/test_curses.py

@@ -3459,6 +3459,8 @@ def test_use_prescr_screen(self):
             with self.assertRaises(curses.error):
                 prescr.use(func)
         # Affecting the state before initscr() is what such a screen is for.
+        # use_env() is process-wide, not a property of this screen.
+        self.addCleanup(curses.use_env, True)
         prescr.use(lambda scr: curses.use_env(False))
         # The current screen is unchanged.
         screen.stdscr.refresh()