frontend: Remove Etcd radio "required" validator
frontend: Remove Etcd radio "required" validator

This is a radio input with a default value, so the validator is
redundant. We don't use validators like this for our other radio inputs.

derekhiggins/installer,squat/tectonic-installer,kyoto/tectonic-installer,squat/tectonic-installer,lander2k2/tectonic-installer,cpanato/tectonic-installer,kalmog/tectonic-installer,derekhiggins/installer,kyoto/tectonic-installer,kyoto/tectonic-installer,cpanato/tectonic-installer,squat/tectonic-installer,lander2k2/tectonic-installer,kyoto/tectonic-installer,lander2k2/tectonic-installer,cpanato/tectonic-installer,squat/tectonic-installer,cpanato/tectonic-installer,kalmog/tectonic-installer,kalmog/tectonic-installer,kyoto/tectonic-installer,lander2k2/tectonic-installer