Fix google cloud storage with rustls + http2

[saroh]

Remove host http header when using rustls in order for storage.googleapis.com to function with rustls

Hi!
We ran into a error using Rusoto with rustls enabled (quickwit-oss/quickwit#1584). It turns out Google rejects the http2 payload if it contains a host header. This fix feels a little hacky given that google seems to be the only provider to act this way. I can close this PR and open an issue if you prefer :)

Sample code which errors on the current main branch:

use rusoto_core::Region;
use rusoto_s3::{S3Client, S3};

#[tokio::main]
async fn main() {
    let region = Region::Custom {
        name: "gcs".to_string(),
        endpoint: "https://storage.googleapis.com".to_string(),
    };
    let client = S3Client::new(region);
    println!("{:?}", client.list_buckets().await);
}

outputs Err(HttpDispatch(HttpDispatchError { message: "Error obtaining body: Error obtaining chunk: error reading a body from connection: stream error received: unspecific protocol error detected" }))

with this branch: Ok(ListBucketsOutput { buckets: Some([Bucket { creation_date: Some("2022-06-05T18:03:45.929Z"), name: Some("qw-region") }]), owner: None })

It's possible to use rusoto with rustls and GCP using a http1 client (quickwit-oss/quickwit#1612)

[saroh]

Host header is required for HTTP/1.1 but not HTTP/2 it seems: https://datatracker.ietf.org/doc/html/rfc7540#section-8.1.2.3

It'd be safer/necessary to put this behind a http2 or gcp-http2 feature because this'd break custom clients using HTTP/1 imho.