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# Type of request: This is a ...

[x] bug report
[ ] feature request

# Detailed description
When I call the Lambda PutFunctionEventInvokeConfig API using the aws-java-sdk, the sdk throws an exception claiming it cannot parse the LastModified timestamp in the response:
```
software.amazon.awssdk.core.exception.SdkClientException: Unable to parse date : 2021-05-28T16:02:30.018Z
        at software.amazon.awssdk.core.exception.SdkClientException$BuilderImpl.build(SdkClientException.java:98)
        at software.amazon.awssdk.protocols.core.StringToInstant.lambda$safeParseDate$0(StringToInstant.java:77)
        at software.amazon.awssdk.protocols.core.StringToInstant.convert(StringToInstant.java:54)
        at software.amazon.awssdk.protocols.core.StringToInstant.convert(StringToInstant.java:32)
```

For comparison, the response for a getting a FunctionEventInvokeConfig for a Lambda of a real AWS account using the aws-cli is the following:
```
{
    "LastModified": "2021-05-27T19:26:43.454000-07:00",
    "FunctionArn": "...",
    ...
}
```

## Expected behavior
LambdaAsyncClient in aws-java-sdk should correctly parse the response for a PutFunctionEventInvokeConfig request.

## Actual behavior
LambdaAsyncClient in aws-java-sdk throws an exception when parsing the LastModified field in the response.

# Steps to reproduce

## Command used to start LocalStack
```
docker run -d --rm --name localstack -p 4566:4566 localstack/localstack:latest
```

## Client code (AWS SDK code snippet, or sequence of "awslocal" commands)
```
val putEventInvokeConfigRequest =
  PutFunctionEventInvokeConfigRequest.builder
    .functionName(functionName)
    .maximumEventAgeInSeconds(21600)
    .maximumRetryAttempts(0)
    .build
lambdaClient.putFunctionEventInvokeConfig(putEventInvokeConfigRequest)
```


data = json.loads(to_str(request.data))
    arn = func_arn(function)
    
    LAMBDA_EXECUTOR.cleanup(arn)
    lambda_details = region.lambdas.get(arn)
    if not lambda_details:
        return error_response('Unable to find Lambda function ARN "%s"' % arn,
            404, error_type='ResourceNotFoundException')
    if data.get('Handler'):
        lambda_details.handler = data['Handler']
    if data.get('Runtime'):
        lambda_details.runtime = data['Runtime']
    lambda_details.set_dead_letter_config(data)
    env_vars = data.get('Environment', {}).get('Variables')
    if env_vars is not None:
        lambda_details.envvars = env_vars
    if data.get('Timeout'):
        lambda_details.timeout = data['Timeout']
    if data.get('Role'):
        lambda_details.role = data['Role']
    if data.get('MemorySize'):
        lambda_details.memory_size = data['MemorySize']
    if data.get('Description'):
        lambda_details.description = data['Description']
    if data.get('VpcConfig'):
        lambda_details.vpc_config = data['VpcConfig']
    if data.get('KMSKeyArn'):
        lambda_details.kms_key_arn = data['KMSKeyArn']
    return jsonify(data)
def generate_policy_statement(sid, action, arn, sourcearn, principal):