Check if we still need this Proguard rule

```
# Without this the playback notification doesn't show up on fresh launch
# https://github.com/shiftyjelly/pocketcasts-android/issues/1656
-keep class au.com.shiftyjelly.pocketcasts.core.player.** { *; }
```
This has now been moved to the package: au.com.shiftyjelly.pocketcasts.repositories.playback

**Below is issue 1656**

Notifications - Media control notification doesn't appear in certain conditions

**Steps to Replicate**

1. Clear app storage.
2. Start the app.
3. Tap on a podcast.
4. Choose an episode and tap on the playback icon.
5. Verify that the Pocket Cast icon is shown on the status bar.
6. Next, pull the notification drawer and check if the media controls are visible.
7. Then, lock the screen by pressing the power button.
8. Verify that the media control is also visible.

**Observations**
- No Pocket Cast icon on the status bar.
- Media Control notification is not seen from the notification drawer nor the lockscreen.
- When I force-stop the app, restarted, and did the same steps again then the status bar icon and media controls are seen.

Locate the Proguard configuration containing the keep rule for au.com.shiftyjelly.pocketcasts.core.player.** and compare it with the moved au.com.shiftyjelly.pocketcasts.repositories.playback package. Reproduce the issue 1656 steps after checking the rule, and consider the work done when the rule's necessity is established without regressing the playback notification.

Written by the indexing model from the issue text.