### 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_
}
                        ],
                    }
                )
            output = {
                "jobName": job_name,
                "status": TranscriptionJobStatus.COMPLETED,
                "results": {
                    "transcripts": [
                        {
                            "transcript": tc_result["text"],
                        }
                    ],
                    "items": items,
                },
            }
            
            output_key = short_uid() + ".json"
            s3_client.put_object(Bucket=bucket, Key=output_key, Body=json.dumps(output))
            
            job["CompletionTime"] = datetime.datetime.utcnow()
            job["TranscriptionJobStatus"] = TranscriptionJobStatus.COMPLETED
            job["Transcript"] = Transcript(TranscriptFileUri=f"s3://{bucket}/{output_key}")
            job["MediaFormat"] = MediaFormat.wav
            LOG.info("Transcription job completed: %s", job_name)
        except Exception as exc:
            job["FailureReason"] = failure_reason or str(exc)
            job["TranscriptionJobStatus"] = TranscriptionJobStatus.FAILED
            LOG.exception("Transcription job %s failed: %s", job_name, job["FailureReason"])