Remove assumption that an environment request has the cluster label

[t-persson]

Description

When creating environment requests for ETOS, it is expected that the cluster label is set, but if we want to be able to use the environmentrequests for other services in the future, we may want to remove that expectation.

Additional Context

No response

Further links

https://github.com/eiffel-community/etos/blob/main/internal/controller/environmentrequest_controller.go#L216