Do not set Host header in proxied request

If there is a reverse proxy downstream of hyper-reverse-proxy, and
the forward_url is something like `http://127.0.0.1:4333`, with the
expectation that the downstream RP will handle the request further, then
the request ends up with `Host: 127.0.0.1` as a header, which is
incorrect. It's seemingly impossible to override this behavior.

Removing the setting of the Host header to fix this, as it's not
necessary anyway.

src/lib.rs

@@ -3,7 +3,7 @@
 #[macro_use]
 extern crate tracing;
 
-use hyper::header::{HeaderMap, HeaderName, HeaderValue, HOST};
+use hyper::header::{HeaderMap, HeaderName, HeaderValue};
 use hyper::http::header::{InvalidHeaderValue, ToStrError};
 use hyper::http::uri::InvalidUri;
 use hyper::upgrade::OnUpgrade;
@@ -225,9 +225,9 @@ fn create_proxied_request<B>(
 
     debug!("Setting headers of proxied request");
 
-    request
-        .headers_mut()
-        .insert(HOST, HeaderValue::from_str(uri.host().unwrap())?);
+    //request
+    //    .headers_mut()
+    //    .insert(HOST, HeaderValue::from_str(uri.host().unwrap())?);
 
     *request.uri_mut() = uri;