- When attempting to remove a created lambda permission with the new fix from https://github.com/localstack/localstack/issues/1260, throws up `SerializationError`

Code being called:

```
func deleteLambdaPermission(ctx context.Context, destinationLambdaARN, permissionStatementID string) (err error) {
	lambdaClient := services.LambdaClient()
	lambdaRemovePermissionInput := &lambda.RemovePermissionInput{
		FunctionName: aws.String(destinationLambdaARN),
		StatementId:  aws.String(permissionStatementID),
	}
	_, err = lambdaClient.RemovePermissionWithContext(ctx, lambdaRemovePermissionInput)

	return
}
```

Checking for error in tests shows the following

```
 Expected
        <*awserr.requestError | 0xc0004a2180>: {
            awsError: {
                code: "SerializationError",
                message: "failed to unmarshal response error",
                errs: [
                    {
                        awsError: {
                            code: "UnmarshalError",
                            message: "failed decoding error message",
                            errs: [
                                {
                                    msg: "invalid character '<' looking for beginning of value",
                                    Offset: 1,
                                },
                            ],
                        },
                        bytes: [60, 33, 68, 79, 67, 84, 89, 80, 69, 32, 72, 84, 77, 76, 32, 80, 85, 66, 76, 73, 67, 32, 34, 45, 47, 47, 87, 51, 67, 47, 47, 68, 84, 68, 32, 72, 84, 77, 76, 32, 51, 46, 50, 32, 70, 105, 110, 97, 108, 47, 47, 69, 78, 34, 62, 10, 60, 116, 105, 116, 108, 101, 62, 52, 48, 52, 32, 78, 111, 116, 32, 70, 111, 117, 110, 100, 60, 47, 116, 105, 116, 108, 101, 62, 10, 60, 104, 49, 62, 78, 111, 116, 32, 70, 111, 117, 110, 100, 60, 47, 104, 49, 62, 10, 60, 112, 62, 84, 104, 101, 32, 114, 101, 113, 117, 101, 115, 116, 101, 100, 32, 85, 82, 76, 32, 119, 97, 115, 32, 110, 111, 116, 32, 102, 111, 117, 110, 100, 32, 111, 110, 32, 116, 104, 101, 32, 115, 101, 114, 118, 101, 114, 46, 32, 73, 102, 32, 121, 111, 117, 32, 101, 110, 116, 101, 114, 101, 100, 32, 116, 104, 101, 32, 85, 82, 76, 32, 109, 97, 110, 117, 97, 108, 108, 121, 32, 112, 108, 101, 97, 115, 101, 32, 99, 104, 101, 99, 107, 32, 121, 111, 117, 114, 32, 115, 112, 101, 108, 108, 105, 110, 103, 32, 97, 110, 100, 32, 116, 114, 121, 32, 97, 103, 97, 105, 110, 46, 60, 47, 112, 62, 10],
                    },
                ],
            },
            statusCode: 404,
            requestID: "",
            bytes: nil,
        }
    to be nil
```
version=LOCALSTACK_MAVEN_VERSION, url=MAVEN_BASE_URL, name='localstack-utils')
TEST_LAMBDA_LIBS = ['localstack', 'localstack_client', 'requests',
    'psutil', 'urllib3', 'chardet', 'certifi', 'idna', 'pip', 'dns']
class LambdaTestBase(unittest.TestCase):
    def check_lambda_logs(self, func_name, expected_lines=[]):
        logs_client = aws_stack.connect_to_service('logs')
        log_group_name = '/aws/lambda/%s' % func_name
        streams = logs_client.describe_log_streams(logGroupName=log_group_name)['logStreams']
        streams = sorted(streams, key=lambda x: x['creationTime'], reverse=True)
        log_events = logs_client.get_log_events(
            logGroupName=log_group_name, logStreamName=streams[0]['logStreamName'])['events']
        log_messages = [e['message'] for e in log_events]
        for line in expected_lines:
            if '.*' in line:
                found = [re.match(line, m) for m in log_messages]
                if any(found):
                    continue
            self.assertIn(line, log_messages)
class TestLambdaBaseFeatures(unittest.TestCase):
    def test_forward_to_fallback_url_dynamodb(self):
        db_table = 'lambda-records'
        ddb_client = aws_stack.connect_to_service('dynamodb')
        def num_items():
            return len((run_safe(ddb_client.scan, TableName=db_table) or {'Items': []})['Items'])
        items_before = num_items()
        self._run_forward_to_fallback_url('dynamodb://%s' % db_table)
        items_after = num_items()
        self.assertEqual(items_after, items_before + 3)
    def test_forward_to_fallback_url_http(self):
        class MyUpdateListener(ProxyListener):