Estimate content position when playWhenReady never has changed

This change closes an edge case when an app is connecting a controller to a session that is already playing. In such a case `MediaControllerImplBase.getContentPosition()` keeps returning the first estimation for every call until `playWhenReady` changes for the first time.

Reproduction: Launch the demo-session app and start audio playback. Put the activity to the background and then to the foreground again. Go to the playlist view and `PlayerActivity` without interrupting playback and try to seek in the timebar. The position is stuck and snaps back.
PiperOrigin-RevId: 422795360

libraries/session/src/main/java/androidx/media3/session/MediaControllerImplBase.java

@@ -677,8 +677,7 @@ import org.checkerframework.checker.nullness.qual.NonNull;
   @Override
   public long getContentPosition() {
     boolean receivedUpdatedPositionInfo =
-        lastSetPlayWhenReadyCalledTimeMs != C.TIME_UNSET
-            && lastSetPlayWhenReadyCalledTimeMs < playerInfo.sessionPositionInfo.eventTimeMs;
+        lastSetPlayWhenReadyCalledTimeMs < playerInfo.sessionPositionInfo.eventTimeMs;
     if (!playerInfo.isPlaying || playerInfo.sessionPositionInfo.isPlayingAd) {
       if (receivedUpdatedPositionInfo || lastReturnedContentPositionMs == C.TIME_UNSET) {
         lastReturnedContentPositionMs =