examples/rps/internal: Fix username
examples/rps/internal: Fix username

Use os.user.Current() instead of relying on the USER env variable to
construct the default name to publish.

Change-Id: Ib02ae7c34044d58e3e31d27abfff67d057da5521

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