add try/except for wait_for_frame call for CP5.0 caompatibility

Author: jerryneedell

adafruit_slideshow.py

@@ -320,7 +320,12 @@ def advance(self):
             sprite = self._sprite_class(odb,
                                         pixel_shader=displayio.ColorConverter(), position=(0, 0))
         self._group.append(sprite)
-        self._display.wait_for_frame()
+        # wait_for_frame is no longer needed in CP5.0
+        # use try/except for backward compatibility
+        try:
+            self._display.wait_for_frame()
+        except AttributeError:
+            pass
 
         self._fade_up()
         self._img_start = time.monotonic()