Adding app label to spec.selector

[pablogarciamiranda]

Simple fix to add the app.kubernetes.io/name: netbox-operator to the spec.selector so it can be used for filtering logs properly.

[faebr]

LGTM
We will need to add a note to the next release notes since this label is not mutable. Which means that if netbox-operator is deployed using for example flux, one needs to manually delete the deployment.