SigV4 returns wrong error for mismatched date and signed-date

[arielshaqed]

When the date in the signed credentials on a SigV4 request does not match the date (or x-amz-date) on the message we return ErrMalformedCredentialDate (see function getAmzDate).

In fact we should return an explanatory SignatureDoesNotMatch. See https://docs.aws.amazon.com/general/latest/gr/signature-v4-troubleshooting.html, starting with text:

The date that you use as part of the credential must match the date value in the x-amz-date header.

[github-actions[bot]]

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[arielshaqed]

Still an error, and users will have a harder time debugging some integrations.