[4.0.0] HX-Preload: HX-Request-Type missing

[dirkjonker]

It seems that the HX-Request-Type header is not added for requests with preload.

How to reproduce:

1. Go to https://four.htmx.org/
2. Open devtools, network tab
3. Hover on any menu item in the top to trigger HTMX preload
4. Observe that HX-Request-Type header is missing
5. Wait 5 seconds to let the preloaded response expire
6. Click the link to let HTMX do a regular request
7. Observe that this request does include the HX-Request-Type header