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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.

def api_name(self):
        return 'sns'
    def forward_request(self, method, path, data, headers):
        if method == 'OPTIONS':
            return 200
        
        try:
            aws_stack.check_valid_region(headers)
            aws_stack.set_default_region_in_headers(headers)
        except Exception as e:
            return make_error(message=str(e), code=400)
        if method == 'POST':
            
            req_data = urlparse.parse_qs(to_str(data), keep_blank_values=True)
            
            if not req_data:
                parsed_path = urlparse.urlparse(path)
                req_data = urlparse.parse_qs(parsed_path.query, keep_blank_values=True)
            req_action = req_data['Action'][0]
            topic_arn = req_data.get('TargetArn') or req_data.get('TopicArn') or req_data.get('ResourceArn')
            if topic_arn:
                topic_arn = topic_arn[0]
                topic_arn = aws_stack.fix_account_id_in_arns(topic_arn)
            if req_action == 'SetSubscriptionAttributes':
                sub = get_subscription_by_arn(req_data['SubscriptionArn'][0])
                if not sub:
                    return make_error(message='Unable to find subscription for given ARN', code=400)