message: fix comment and remove unused const
diff: @@ -253,7 +253,6 @@ module.exports = React.createClass({
  },
  _getEventTiles: function() {
  - const EventTile = sdk.getComponent('rooms.EventTile');
  const DateSeparator = sdk.getComponent('messages.DateSeparator');
  const MemberEventListSummary = sdk.getComponent('views.elements.MemberEventListSummary');
  @@ -263,7 +262,7 @@ module.exports = React.createClass({
  // first figure out which is the last event in the list which we're
  // actually going to show; this allows us to behave slightly
  - // differently for the last event in the list. (eg show timestamps)
  + // differently for the last event in the list. (eg show timestamp)
  //
  // we also need to figure out which is the last event we show which isn't
  // a local echo, to manage the read-marker.
  