[Device-Roaming-Subscription]: Protocol components are missing in specification

[maxl2287]

Describe the bug
The components described in the descriminator for the prototocol-property are missing.
This causes problems with our code-generator and makes it unpossible to create the expected property-models.

See:

      discriminator:
        propertyName: protocol
        mapping:
          HTTP: "#/components/schemas/HTTPSubscriptionRequest"
          MQTT3: "#/components/schemas/MQTTSubscriptionRequest"
          MQTT5: "#/components/schemas/MQTTSubscriptionRequest"
          AMQP: "#/components/schemas/AMQPSubscriptionRequest"
          NATS: "#/components/schemas/NATSSubscriptionRequest"
          KAFKA: "#/components/schemas/ApacheKafkaSubscriptionRequest"

Tested with r1.2 - device-roaming-status-subscriptions.yaml
Expected behavior
The components should be there, otherwise the yaml is invalid.

[hdamker]

cc: @camaraproject/commonalities_maintainers