Remove Namespace parameter from kubeplus kubectl plugins

[devdattakulkarni]

Currently the input for the following kubeplus kubectl plugins takes in the Namespace as one of the parameters. The value to be provided is the name of the Namespace in which the app instance is created. App instances are supposed to be created in the same namespace as KubePlus's namespace. This namespace can be determined by plugins on their end. So there is no need to pass in the Namespace parameter.

kubectl applogs
kubectl appurl
kubectl grantpermission consumer
kubectl retrieve kubeconfig consumer
kubectl retrieve kubeconfig provider