fix: read relation tuples must require namspace query parameter only

[jan-moxter]

The API spec is created automatically from code comments. By reusing the queryRelationTuple from transact_server.go in read_server.go the query parameters object and relation where marked required. This PR copies the queryRelationTuple to read_server.go and removes the required.
The spec where recreated by running make sdk

Related issue(s)

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Further Comments

[zepatrik]

Very nice, thank you 👍
The namespace should also not be required as far as I can tell from the code, but I think that needs some update to the docs as well so tracking as an individual issue #761