deployments: deployments instructions contains deployment ID instead of device deployment ID

When the device is asking for an update, and there is an active deployment targeting this device, the device will get 200 response with deployment instructions.
According to the documentation, instructions should include the
id which is Deployment ID (device unique)
The intention here was that it will be an identifier of the instance of the deployment for particular device. That's why we say in the docs it's device unique.

Acceptance criteria:

• Update the documentation to state that the ID is the Deployment ID (drop "device unique")