Tiny cleanup: remove an extra "thread" in the comment for ExoPlayer interface.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=207124509

library/core/src/main/java/com/google/android/exoplayer2/ExoPlayer.java

@@ -93,7 +93,7 @@ import com.google.android.exoplayer2.video.MediaCodecVideoRenderer;
  *       #getApplicationLooper()}. This Looper can be specified when creating the player, or this is
  *       #getApplicationLooper()}. This Looper can be specified when creating the player, or this is
  *       the Looper of the thread the player is created on, or the Looper of the application's main
  *       the Looper of the thread the player is created on, or the Looper of the application's main
  *       thread if the player is created on a thread without Looper.
  *       thread if the player is created on a thread without Looper.
- *   <li>Registered listeners are called on the thread thread associated with {@link
+ *   <li>Registered listeners are called on the thread associated with {@link
  *       #getApplicationLooper()}. Note that this means registered listeners are called on the same
  *       #getApplicationLooper()}. Note that this means registered listeners are called on the same
  *       thread which must be used to access the player.
  *       thread which must be used to access the player.
  *   <li>An internal playback thread is responsible for playback. Injected player components such as
  *   <li>An internal playback thread is responsible for playback. Injected player components such as