Fix server shutdown documentation

[veeceey]

Summary

Updates the HTTP server shutdown documentation to include the server.server_close() call, which is required to properly release the port and allow the server to be restarted on the same port.

Problem

Without calling server.server_close(), attempting to restart the server on the same port results in an OSError: [Errno 98] Address already in use error.

Changes

• Added server.server_close() call to the server shutdown example in the HTTP documentation

Test Plan

Manual Testing:
Created and ran a test script that:

1. Starts a server on port 8000
2. Shuts it down using both shutdown() and server_close()
3. Restarts the server on the same port
4. Shuts it down again

Before fix:

server, t = start_http_server(8000)
server.shutdown()
t.join()
server, t = start_http_server(8000)  # OSError: Address already in use

After fix:

server, t = start_http_server(8000)
server.shutdown()
server.server_close()
t.join()
server, t = start_http_server(8000)  # Works!

The test passes successfully with the updated documentation.

Fixes #1068

[csmarchbanks]

Thanks!