fix: to schedule the close connection task to run in the channel's ev…

…ent loop

core/src/main/java/com/linecorp/armeria/server/HttpServerHandler.java

@@ -781,7 +781,7 @@ private void handleRequestOrResponseComplete() {
  // Stop receiving new requests.
  handledLastRequest = true;
  if (unfinishedRequests.isEmpty()) {
- ctx.executor().schedule(() ->
+ ctx.channel().eventLoop().schedule(() ->
  ctx.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(CLOSE),
  Flags.defaultHttp1ConnectionCloseDelayMillis(), TimeUnit.MILLISECONDS);
  }