Simplify DefaultDrmSession event handling

- Handling EVENT_PROVISION_REQUIRED is unnecessary because we handle
  it via NotProvisionedException, which was thrown on all API levels.
- Handling EVENT_KEY_EXPIRED during playback is unnecessary. All it
  does is cause an error to be thrown, but an error will be thrown
  anyway out of the MediaCodec when it tries to use the expired keys.
  It's currently a race condition where the error gets thrown from,
  where-as having it always be thrown from one place is preferable.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=219172021

library/core/src/main/java/com/google/android/exoplayer2/drm/DefaultDrmSession.java

@@ -207,18 +207,11 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
     return Arrays.equals(this.sessionId, sessionId);
   }
 
-  @SuppressWarnings("deprecation")
   public void onMediaDrmEvent(int what) {
     switch (what) {
-      case ExoMediaDrm.EVENT_PROVISION_REQUIRED:
-        onProvisionRequired();
-        break;
       case ExoMediaDrm.EVENT_KEY_REQUIRED:
         onKeysRequired();
         break;
-      case ExoMediaDrm.EVENT_KEY_EXPIRED:
-        onKeysExpired();
-        break;
       default:
         break;
     }
@@ -434,23 +427,10 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
     }
   }
 
-  private void onProvisionRequired() {
-    if (mode == DefaultDrmSessionManager.MODE_PLAYBACK && isOpen()) {
-      state = STATE_OPENED;
-      provisioningManager.provisionRequired(this);
-    }
-  }
-
   private void onKeysRequired() {
-    if (mode == DefaultDrmSessionManager.MODE_PLAYBACK && isOpen()) {
-      doLicense(/* allowRetry= */ false);
-    }
-  }
-
-  private void onKeysExpired() {
     if (mode == DefaultDrmSessionManager.MODE_PLAYBACK && state == STATE_OPENED_WITH_KEYS) {
-      state = STATE_OPENED;
-      onError(new KeysExpiredException());
+      Util.castNonNull(sessionId);
+      doLicense(/* allowRetry= */ false);
     }
   }