fix(Player): allow fast-forward for all playback speeds

Ref: https://github.com/libre-tube/LibreTube/pull/8122/changes#r2738259942
Ref: https://github.com/androidx/media/blob/01c37572827dc77543fe6d0deda3efe06ec95f61/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/audio/DefaultAudioSink.java#L520

Author: FineFindus

app/src/main/java/com/github/libretube/helpers/PlayerHelper.kt

@@ -73,7 +73,7 @@ object PlayerHelper {
     /**
      * Maximum playback speed supported by ExoPlayer
      */
-    const val MAXIMUM_PLAYBACK_SPEED = 4f
+    const val MAXIMUM_PLAYBACK_SPEED = 8f
 
     /**
      * The maximum amount of time to wait until the video starts playing: 10 minutes