Wrong `RequestResponseCode` in fuzzing test

[steven-bellock]

https://github.com/DMTF/libspdm/blob/main/unit_test/fuzzing/test_responder/test_spdm_responder_encap_response/encap_response.c exercises both libspdm_get_response_encapsulated_request() and libspdm_get_response_encapsulated_response_ack(). libspdm_get_response_encapsulated_request should only be called when the RequestResponseCode is GET_ENCAPSULATED_REQUEST, and libspdm_get_response_encapsulated_response_ack should only be called when the RequestResponseCode is DELIVER_ENCAPSULATED_RESPONSE. However the test does not distinguish between the seed files in https://github.com/DMTF/libspdm/tree/main/unit_test/fuzzing/seeds/test_spdm_responder_encap_response.