remove reference to deprecated networking plugin
remove reference to deprecated networking plugin

- the core cli now has the network-policy functionality

[#160364892]

Signed-off-by: Christian Ang <15ae83feccf4d84083a62aba1cdf46bd8ce2e33b@pivotal.io>

kkellner/cli-plugin-repo,kkellner/cli-plugin-repo,cloudfoundry-incubator/cli-plugin-repo,cloudfoundry-incubator/cli-plugin-repo,kkellner/cli-plugin-repo,cloudfoundry-incubator/cli-plugin-repo,cloudfoundry-incubator/cli-plugin-repo