remove `rev` line from `lakefile.toml`

[fpvandoorn]

With a rev line, lake update doesn't do anything, which is confusing for new users.
I recommend either removing the rev line or changing it to something like master (or something like stable, if that exists?) so that lake update goes to the newest (or almost newest) version?

[pitmonticone]

Yes, that is definitely a mistake. Noticed a few minutes before starting a new blueprint-driven project.

Sorry!

[fpvandoorn]

Thanks!