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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)
```


def delete_function_event_invoke_config(function):
    region = LambdaRegion.get()
    try:
        function_arn = func_arn(function)
        lambda_obj = region.lambdas[function_arn]
    except Exception as e:
        return error_response(str(e), 400)
    lambda_obj.clear_function_event_invoke_config()
    return Response('', status=204)
@app.route('/2020-06-30/functions/<function>/code-signing-config', methods=['GET'])
def get_function_code_signing_config(function):
    region = LambdaRegion.get()
    function_arn = func_arn(function)
    if function_arn not in region.lambdas:
        msg = 'Function not found: %s' % (function_arn)
        return error_response(msg, 404, error_type='ResourceNotFoundException')
    lambda_obj = region.lambdas[function_arn]
    if not lambda_obj.code_signing_config_arn:
        arn = None
        function = None
    else:
        arn = lambda_obj.code_signing_config_arn
    result = {
        'CodeSigningConfigArn': arn,
        'FunctionName': function
    }
    return Response(json.dumps(result), status=200)
@app.route('/2020-06-30/functions/<function>/code-signing-config', methods=['PUT'])
def put_function_code_signing_config(function):
    region = LambdaRegion.get()