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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.

for topic_arn, existing_subs in SNS_SUBSCRIPTIONS.items():
        SNS_SUBSCRIPTIONS[topic_arn] = [
            sub for sub in existing_subs
            if sub['SubscriptionArn'] != subscription_arn
        ]
def _get_tags(topic_arn):
    if topic_arn not in SNS_TAGS:
        SNS_TAGS[topic_arn] = []
    return SNS_TAGS[topic_arn]
def do_list_tags_for_resource(topic_arn):
    return _get_tags(topic_arn)
def do_tag_resource(topic_arn, tags):
    existing_tags = SNS_TAGS.get(topic_arn, [])
    tags = [
        tag for idx, tag in enumerate(tags)
        if tag not in tags[:idx]
    ]
    def existing_tag_index(item):
        for idx, tag in enumerate(existing_tags):
            if item['Key'] == tag['Key']:
                return idx
        return None
    for item in tags:
        existing_index = existing_tag_index(item)
        if existing_index is None:
            existing_tags.append(item)
        else:
            existing_tags[existing_index] = item
    SNS_TAGS[topic_arn] = existing_tags
def do_untag_resource(topic_arn, tag_keys):