### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

Initiating a multipart S3 upload to LocalStack returns an XML document with a root element CreateMultipartUploadOutput. This causes an error in the ex_aws_s3 library I'm using. We've used the combination of LocalStack + ex_aws_s3 successfully for a few years and the error started occurring a few days ago.

### Expected Behavior

The element should be called InitiateMultipartUploadResult.

### How are you starting LocalStack?

With a `docker run` command

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    docker run -p 4566:4566 localstack/localstack

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

    aws --debug --endpoint-url=http://localhost:4566 s3api create-multipart-upload --bucket my-bucket --key 'multipart/01'


### Environment

```markdown
- OS: Ubuntu 20.04.5 LTS
- LocalStack: latest
```


### Anything else?

S3 docs specifying InitiateMultipartUploadResult:
https://docs.aws.amazon.com/AmazonS3/latest/API/API_CreateMultipartUpload.html

Reference in official AWS Java client:
https://github.com/aws/aws-sdk-java/blob/ef22b94750d4c155d74b09012b3be5d9d98bbd33/aws-java-sdk-s3/src/main/java/com/amazonaws/services/s3/model/transform/XmlResponsesSaxParser.java#L1865

Where our particular error gets raised in ex_aws_s3:
https://github.com/ex-aws/ex_aws_s3/blob/7e12f2b0578b2620c047d2e44c40a6de8773584a/lib/ex_aws/s3/parsers.ex#L78
"""
    Validate the canned ACL value, or raise an Exception
    """
    if canned_acl and not is_canned_acl_bucket_valid(canned_acl):
        ex = _create_invalid_argument_exc(None, "x-amz-acl", canned_acl)
        raise ex
def validate_grantee_in_headers(grant: str, grantees: str) -> None:
    splitted_grantees = [grantee.strip() for grantee in grantees.split(",")]
    for grantee in splitted_grantees:
        grantee_type, grantee_id = grantee.split("=")
        grantee_id = grantee_id.strip('"')
        if grantee_type not in ("uri", "id", "emailAddress"):
            ex = _create_invalid_argument_exc(
                "Argument format not recognized", get_header_name(grant), grantee
            )
            raise ex
        elif grantee_type == "uri" and grantee_id not in s3_constants.VALID_ACL_PREDEFINED_GROUPS:
            ex = _create_invalid_argument_exc("Invalid group uri", "uri", grantee_id)
            raise ex
        elif grantee_type == "id" and not is_valid_canonical_id(grantee_id):
            ex = _create_invalid_argument_exc("Invalid id", "id", grantee_id)
            raise ex
        elif grantee_type == "emailAddress":
            
            continue
def validate_acl_acp(acp: AccessControlPolicy) -> None: