message: Fix display name change message
  (i18n file fixes coming separately for ease of review)
  Fixes
diff: @@ -52,8 +52,7 @@ function textForMemberEvent(ev) {
  case 'join':
  if (prevContent && prevContent.membership === 'join') {
  if (prevContent.displayname && content.displayname && prevContent.displayname !== content.displayname) {
  - return _t('%(senderName)s changed their display name from %(oldDisplayName)s to %(displayName)s.', {
  - senderName,
  + return _t('%(oldDisplayName)s changed their display name to %(displayName)s.', {
  oldDisplayName: prevContent.displayname,
  displayName: content.displayname,
  });
  