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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.

'Content-Type': 'text/plain',
                        
                        
                        'x-amz-sns-message-type': msg_type,
                        'x-amz-sns-topic-arn': subscriber['TopicArn'],
                        'x-amz-sns-subscription-arn': subscriber['SubscriptionArn'],
                        'User-Agent': 'Amazon Simple Notification Service Agent'
                    },
                    data=message_body,
                    verify=False
                )
                response.raise_for_status()
            except Exception as exc:
                LOG.info('Received error on sending SNS message, putting to DLQ (if configured): %s' % exc)
                sns_error_to_dead_letter_queue(subscriber['SubscriptionArn'], req_data, str(exc))
        elif subscriber['Protocol'] == 'application':
            try:
                sns_client = aws_stack.connect_to_service('sns')
                sns_client.publish(TargetArn=subscriber['Endpoint'], Message=message)
            except Exception as exc:
                LOG.warning('Unable to forward SNS message to SNS platform app: %s %s' % (exc, traceback.format_exc()))
                sns_error_to_dead_letter_queue(subscriber['SubscriptionArn'], req_data, str(exc))
        elif subscriber['Protocol'] == 'email':
            ses_client = aws_stack.connect_to_service('ses')
            if subscriber.get('Endpoint'):
                ses_client.verify_email_address(EmailAddress=subscriber.get('Endpoint'))
                ses_client.verify_email_address(EmailAddress='admin@localstack.com')
                ses_client.send_email(Source='admin@localstack.com',
                                      Message={'Body': {'Text': {'Data': message}},
                                               'Subject': {'Data': 'SNS-Subscriber-Endpoint'}},