fix backgrounds and remove CP6 compatibility

Author: FoamyGuy

adafruit_pyoa.py

@@ -401,22 +401,12 @@ def set_background(self, filename, *, with_fade=True):
             self._background_group.pop()
 
         if filename:
-            if self._background_file:
-                self._background_file.close()
-            with open(
-                self._gamedirectory + "/" + filename, "rb"
-            ) as self._background_file:
-                # TODO: Once CP6 is no longer supported, pass combined filename into OnDiskBitmap
-                background = displayio.OnDiskBitmap(self._background_file)
-                self._background_sprite = displayio.TileGrid(
-                    background,
-                    pixel_shader=getattr(
-                        background, "pixel_shader", displayio.ColorConverter()
-                    ),
-                    # TODO: Once CP6 is no longer supported, replace the above line with below
-                    # pixel_shader=background.pixel_shader,
-                )
-                self._background_group.append(self._background_sprite)
+            background = displayio.OnDiskBitmap(self._gamedirectory + "/" + filename)
+            self._background_sprite = displayio.TileGrid(
+                background,
+                pixel_shader=background.pixel_shader,
+            )
+            self._background_group.append(self._background_sprite)
         if with_fade:
             self._display.refresh(target_frames_per_second=60)
             self.backlight_fade(1.0)