### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

When starting the transcription job in response job object is null:

<img width="1154" alt="Screenshot 2023-04-03 at 09 21 09" src="https://user-images.githubusercontent.com/454412/229447066-1671f811-da49-478d-bf24-252f30b17699.png">


### Expected Behavior

Response from the real AWS stack - job object is not null

<img width="1161" alt="Screenshot 2023-04-03 at 09 30 13" src="https://user-images.githubusercontent.com/454412/229441498-06125248-3b68-4679-8204-0163e8245db6.png">


### How are you starting LocalStack?

Custom (please describe below)

### Steps To Reproduce

Using test containers, reproducing project can be found here:

https://github.com/kkocel/local-stack-transcribe-repro

### Environment

```markdown
- OS: macOS
- LocalStack: latest
```


### Anything else?

_No response_
def _wait_and_assume_role(role_arn: str, session_name: str = None):
        if not session_name:
            session_name = f"session-{short_uid()}"
        def assume_role():
            return sts_client.assume_role(RoleArn=role_arn, RoleSessionName=session_name)[
                "Credentials"
            ]
        
        keys = retry(assume_role, sleep=5, retries=4)
        return keys
    return _wait_and_assume_role
@pytest.fixture
def create_role(iam_client):
    role_names = []
    def _create_role(**kwargs):
        if not kwargs.get("RoleName"):
            kwargs["RoleName"] = f"role-{short_uid()}"
        result = iam_client.create_role(**kwargs)
        role_names.append(result["Role"]["RoleName"])
        return result
    yield _create_role
    for role_name in role_names: