Deprecate setThrowWhenUsingWrongThread.

This method shouldn't be used anymore since the thread enforcement
is the default already. We still keep it for now to ease the transition
for apps that use ExoPlayer on multiple threads and want to temporarily
disable the enforcement while the threading problems are fixed.

PiperOrigin-RevId: 369440789

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

@@ -1821,7 +1821,10 @@ public class SimpleExoPlayer extends BasePlayer
    * <p>The default is {@code true} and this method will be removed in the future.
    *
    * @param throwsWhenUsingWrongThread Whether to throw when methods are called from a wrong thread.
+   * @deprecated Disabling the enforcement can result in hard-to-detect bugs. Do not use this method
+   *     except to ease the transition while wrong thread access problems are fixed.
    */
+  @Deprecated
   public void setThrowsWhenUsingWrongThread(boolean throwsWhenUsingWrongThread) {
     this.throwsWhenUsingWrongThread = throwsWhenUsingWrongThread;
   }