Update warp to 0.3.2

[joshrotenberg]

This updates warp to the latest release, which happens to fix #1797 by making HEAD requests automatically part of warp::fs::dir routes:

With warp 0.3.1:

# cd guide && mdbook serve ...

$ curl --head localhost:3000/index.html
HTTP/1.1 404 Not Found
content-length: 14598
content-type: text/html
accept-ranges: bytes
last-modified: Mon, 20 Jun 2022 18:53:48 GMT
date: Mon, 20 Jun 2022 18:53:52 GMT

With warp 0.3.2:

# cd guide && mdbook serve ...

$ curl --head localhost:3000/index.html
HTTP/1.1 200 OK
content-length: 17487
content-type: text/html
accept-ranges: bytes
last-modified: Mon, 20 Jun 2022 18:56:24 GMT
date: Mon, 20 Jun 2022 18:56:28 GMT

See https://github.com/seanmonstar/warp/blob/master/CHANGELOG.md#v032-november-9-2021

[ehuss]

Thanks!