title: Notification .setContentText not displayed on Android 10
body: <p>I have a simple expandable notification.</p>
  
  <p>Normal Layout: <br>
  Title<br>
  <strong>Short</strong> Text (.setContentText)<br></p>
  
  <p>Explanded:<br>
  Title<br>
  <strong>Long</strong> Text (.setStyle)<br></p>
  
  <p>In Android 10 (API 29) this does not work anymore as only the long text is partially shown. Take a look at the litte arrows in the top right corner.</p>
  
  <p><a href="https://i.stack.imgur.com/uAaXP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/uAaXP.png" alt="enter image description here"></a></p>
  
  <pre><code>val builder = NotificationCompat.Builder(this, CHANNEL_TEST_ID)
      .setSmallIcon(R.drawable.ic_launcher_background)
      .setContentTitle("This is the title")
      .setContentText("This is the content, which is not displayed in Android 10.")
      .setStyle(NotificationCompat.BigTextStyle().bigText("The only displayed text in Android 10. contentText missing."))
      .setPriority(NotificationCompat.PRIORITY_HIGH) // by channel from Android 8
      .setAutoCancel(true) // Android 8
  
  with(NotificationManagerCompat.from(this)) {
      // notificationId is a unique int for each notification that you must define
      notify(101, builder.build())
  }
  
  private const val CHANNEL_TEST_ID = "TEST"
  private fun createNotificationChannel() {
      // Create the NotificationChannel, but only on API 26+ because
      // the NotificationChannel class is new and not in the support library
      if (Build.VERSION.SDK_INT &gt;= Build.VERSION_CODES.O) {
          val name = "Test"
          val descriptionText = "Test"
          val importance = NotificationManager.IMPORTANCE_HIGH
          val channel = NotificationChannel(CHANNEL_TEST_ID, name, importance).apply {
              description = descriptionText
          }
          // Register the channel with the system
          val notificationManager: NotificationManager =
              getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
          notificationManager.createNotificationChannel(channel)
  
      }
  }    
  </code></pre>
  
  <p>Is this a bug or a feature?</p>