[Workers] Add await writer.close(), otherwise it takes 4m30s to get the response from TCP sockets API

[kyouheicf]

Summary

Add await writer.close(), otherwise it takes 4m30s to get the response from TCP sockets

% date && curl https://abc.xyz.workers.dev && date
Fri Jul 26 14:33:23 JST 2024
...
Fri Jul 26 14:37:53 JST 2024

[kyouheicf]

PCX-12482

[KimJ15]

👋Hi there, we’re going to close this PR. All PRs prior to August 12 need to be reworked due to the platform migration to Astro.