Incorrect host header used for favicon grab if stored on a different host

[gf13579]

httpx version:

1.3.4

Current Behavior:

If a website (example.com) references a favicon stored on a different host (some-cdn.com), httpx fails to download it as it it makes the GET against some-cdn.com but includes host: example.com in the request headers.

Expected Behavior:

httpx downloads the favicon from the second host successfully - by not using the first host in the request headers.

Steps To Reproduce:

1. Run httpx -u https://spirit.com.au/ -favicon and observe the lack of favicon
2. Run the same command but with -json and observe the correct favicon_path
3. Start a web proxy (e.g. Burp) on 8080 and run httpx -u https://spirit.com.au/ -favicon -http-proxy http://localhost:8080
4. Observe that the Host header value is spirit.com.au when it should be assets-global.website-fil...