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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.

attributes = {}
    x = 1
    while True:
        name = req_data.get('MessageAttributes.entry.' + str(x) + '.Name', [None])[0]
        if name is not None:
            attribute = {
                'Type': req_data.get('MessageAttributes.entry.' + str(x) + '.Value.DataType', [None])[0]
            }
            string_value = req_data.get('MessageAttributes.entry.' + str(x) + '.Value.StringValue', [None])[0]
            binary_value = req_data.get('MessageAttributes.entry.' + str(x) + '.Value.BinaryValue', [None])[0]
            if string_value is not None:
                attribute['Value'] = string_value
            elif binary_value is not None:
                attribute['Value'] = binary_value
            attributes[name] = attribute
            x += 1
        else:
            break
    return attributes
def get_subscribe_attributes(req_data):
    attributes = {}
    for key in req_data.keys():
        if '.key' in key:
            attributes[req_data[key][0]] = req_data[key.replace('key', 'value')][0]
    return attributes
def is_number(x):