fix(localization): remove unused playback progress label from localization file

Author: gokadzev

lib/localization/app_en.arb

@@ -144,7 +144,6 @@
   "pickImageFromDevice": "Pick image from device",
   "play": "Play",
   "playNext": "Play next",
-  "playbackProgress": "Playback progress",
   "playlist": "Playlist",
   "playlistAlreadyDownloaded": "Playlist already downloaded",
   "playlistAlreadyExists": "Playlist already exists",