fix s3 expected bucket owner presigning

[lucix-aws]

Tested:

package main

import (
    "context"
    "fmt"
    "io"
    "net/http"
    "net/url"

    "github.com/aws/aws-sdk-go-v2/aws"
    "github.com/aws/aws-sdk-go-v2/config"
    "github.com/aws/aws-sdk-go-v2/service/s3"
)

func main() {
    cfg, err := config.LoadDefaultConfig(context.Background())
    if err != nil {
        panic(err)
    }

    svc := s3.NewFromConfig(cfg)
    presigner := s3.NewPresignClient(svc)
    u, err := presigner.PresignGetObject(context.Background(), &s3.GetObjectInput{
        Bucket:              aws.String("<...>"),
        Key:                 aws.String("<...>"),
        ExpectedBucketOwner: aws.String("<... an account id number that isn't expected>"),
    })
    if err != nil {
        panic(err)
    }

    println(u.URL)
    fmt.Printf("%#v\n", u.SignedHeader)

    uu, _ := url.Parse(u.URL)
    resp, err := http.DefaultClient.Do(&http.Request{
        URL:    uu,
        Header: u.SignedHeader,
    })
    if err != nil {
        panic(err)
    }
    fmt.Println(resp.Status)
    p, _ := io.ReadAll(resp.Body)
    fmt.Println(string(p))
}

with fix the presigned GET response printed is the expected 403.