Fix s3UnwrappedXmlOutput of LocationConstraint

[nomick]

The GetBucketLocation operation differs from other operations as it does not double the LocationConstraint XML tag. See https://smithy.io/2.0/aws/customizations/s3-customizations.html for details. Note that the example at https://docs.aws.amazon.com/AmazonS3/latest/API/API_GetBucketLocation.html is also wrong, as the AWS-Client will also not accept it.

This patch fixes the output form

<LocationConstraint>
   <LocationConstraint>string</LocationConstraint>
</LocationConstraint>

to

<LocationConstraint>string</LocationConstraint>

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