doc: minor campaign updates

Created by: LawnGnome

I did a sweep over the campaign docs just to make sure they're up to date with what we're shipping in Sourcegraph 3.20 and src-cli 3.21. The main thing I noticed was a reference to performing actions as users, which is currently targeted to 3.21, so I've reworded that for now.

@davejrt, if you approve, I'd also like to cherry pick this into 3.20 once it's approved and merged.

Extra double closes #13153 (closed).