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# Type of request: This is a ...

[x] bug report
[ ] feature request

# Detailed description

SNS is unable to forward the message to SQS (non fifo queue) when using the `elasticmq` backend and fails with the following log
```
2021-01-19T09:31:50:WARNING:localstack.services.sns.sns_listener: Unable to forward SNS message to SQS: An error occurred (InvalidParameterValue) when calling the SendMessage operation: Value for parameter MessageGroupId is invalid. The request include parameter that is not valid for this queue type Traceback (most recent call last):

File "/opt/code/localstack/localstack/services/sns/sns_listener.py", line 297, in message_to_subscribers

sqs_client.send_message(

File "/opt/code/localstack/.venv/lib/python3.8/site-packages/botocore/client.py", line 357, in _api_call

return self._make_api_call(operation_name, kwargs)

File "/opt/code/localstack/.venv/lib/python3.8/site-packages/botocore/client.py", line 676, in _make_api_call

raise error_class(parsed_response, operation_name)

botocore.exceptions.ClientError: An error occurred (InvalidParameterValue) when calling the SendMessage operation: Value for parameter MessageGroupId is invalid. The request include parameter that is not valid for this queue type
```
This is likely a regression due to #3435. Tested with the default backend on `0.12.5` and it works as expected. Also works with `elasticmq` backend on `0.12.4`

## Expected behavior

Same behavior with the `elasticmq` backend as with the default backend.

## Actual behavior

Fails on `elasticmq` backend, no SQS message received when SNS message is sent.

# Steps to reproduce

## Command used to start LocalStack

```yaml
  localstack:
    image: localstack/localstack:0.12.5
    ports:
      - 4566:4566
    environment:
      - AWS_DEFAULT_REGION=ap-northeast-1
      - SERVICES=sns,sqs
      - SQS_PROVIDER=elasticmq
```

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

unsubscribe_url = '%s/?Action=Unsubscribe&SubscriptionArn=%s' % (external_url,
                                    subscriber['SubscriptionArn'])
                response = lambda_api.process_sns_notification(
                    subscriber['Endpoint'],
                    topic_arn,
                    subscriber['SubscriptionArn'],
                    message,
                    message_id,
                    message_attributes,
                    unsubscribe_url,
                    subject=req_data.get('Subject', [None])[0]
                )
                if isinstance(response, Response):
                    response.raise_for_status()
                elif isinstance(response, FlaskResponse):
                    if response.status_code >= 400:
                        raise Exception('Error response (code %s): %s' % (response.status_code, response.data))
            except Exception as exc:
                LOG.warning('Unable to run Lambda function on SNS message: %s %s' % (exc, traceback.format_exc()))
                sns_error_to_dead_letter_queue(subscriber['SubscriptionArn'], req_data, str(exc))
        elif subscriber['Protocol'] in ['http', 'https']:
            msg_type = (req_data.get('Type') or ['Notification'])[0]
            try:
                message_body = create_sns_message_body(subscriber, req_data, message_id)
            except Exception:
                continue
            try:
                response = requests.post(
                    subscriber['Endpoint'],
                    headers={