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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)
```


for p in policies:
        
        versions = iam_client.list_policy_versions(PolicyArn=p['Arn'])['Versions']
        default_version = [v for v in versions if v.get('IsDefaultVersion')]
        versions = default_version or versions
        doc = versions[0]['Document']
        doc = doc if isinstance(doc, dict) else json.loads(doc)
        if not isinstance(doc['Statement'], list):
            doc['Statement'] = [doc['Statement']]
        for stmt in doc['Statement']:
            stmt['Principal'] = stmt.get('Principal') or {'AWS': TEST_AWS_ACCOUNT_ID}
        doc['PolicyArn'] = p['Arn']
        doc['Id'] = 'default'
        docs.append(doc)
    res_qualifier = func_qualifier(function, qualifier)
    policy = [d for d in docs if d['Statement'][0]['Resource'] == res_qualifier]
    return (policy or [None])[0]
def lookup_function(function, region, request_url):
    result = {
        'Configuration': function,
        'Code': {
            'Location': '%s/code' % request_url
        },
        'Tags': function['Tags']
    }
    lambda_details = region.lambdas.get(function['FunctionArn'])
    if lambda_details.concurrency is not None:
        result['Concurrency'] = lambda_details.concurrency
    return jsonify(result)
def not_found_error(ref=None, msg=None):