[oximeter] Update running instructions for oximeter in simulated environment

[smklein]

Fixes: #1295 by restoring example configs from #1237

Tested by running:

$ cargo run --bin omicron-dev -- db-run
$ cargo run --bin omicron-dev -- ch-run
$ cargo run --bin=nexus -- nexus/examples/config.toml
$ cargo run --bin=sled-agent-sim -- $(uuidgen) [::1]:12345 127.0.0.1:12221
$ cargo run --bin=oximeter run --id $(uuidgen) --address [::1]:12223 -- oximeter/collector/config.toml

And observing that registration completes successfully between Nexus / Oximeter.