naming/endpoint: Remove support of endpoint version 5.
naming/endpoint: Remove support of endpoint version 5.

It should all be switched by now.

Change-Id: Iaa0e34e68a4285eac3302315bd7a4d13bbc23ecc

vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref