message: fix(omemo): do not attach thumbnail
diff: @@ -150,13 +150,6 @@ export default class Omemo {
  public encrypt(contact: Contact, message: Message, xmlElement: Strophe.Builder) {
  let peer = this.getPeer(contact.getJid());
  let plaintextMessage = message.getPlaintextMessage();
  - let attachment = message.getAttachment();
  -
  - if (plaintextMessage.indexOf('aesgcm://') === 0 && attachment && attachment.hasThumbnailData()) {
  - let thumbnailData = attachment.getThumbnailData().replace(/^[^,],+/, '');
  -
  - plaintextMessage = plaintextMessage.replace(/^(aesgcm:[^\n]+)/, '$1\n' + thumbnailData);
  - }
  return peer.encrypt(this.localPeer, plaintextMessage).then((encryptedMessages) => {
  let stanza = Stanza.buildEncryptedStanza(encryptedMessages, this.store.getLocalDeviceId());
  