We can delete the LimitRange resource with the subcommand delete. Like creating the LimitRange, deleting a LimitRange in a Namespace would remove the constraints in the Namespace automatically:

$ kubectl delete -f my-first-limitrange.yaml -n=my-namespace
limitrange "my-limitrange" deleted
$ kubectl describe ns my-namespace
Name:         my-namespace
Labels:       <none>
Annotations:  <none>
Status:       Active

No resource quota.

No resource limits.