fix more private field accesses in tests

Author: t3chguy

test/DecryptionFailureTracker-test.js

@@ -30,9 +30,7 @@ function createFailedDecryptionEvent() {
  const event = new MatrixEvent({
  event_id: "event-id-" + Math.random().toString(16).slice(2),
  });
- event._setClearData(
- event._badEncryptedMessage(":("),
- );
+ event.setClearData(event.badEncryptedMessage(":("));
  return event;
 }
 
@@ -67,7 +65,7 @@ describe('DecryptionFailureTracker', function() {
  tracker.eventDecrypted(decryptedEvent, err);
 
  // Indicate successful decryption: clear data can be anything where the msgtype is not m.bad.encrypted
- decryptedEvent._setClearData({});
+ decryptedEvent.setClearData({});
  tracker.eventDecrypted(decryptedEvent, null);
 
  // Pretend "now" is Infinity