onboarding: Fix typos in comments (#37541)

This PR fixes some grammatical typos in some comments in the
`onboarding` crate.

Release Notes:

- N/A
473bbd78ccMarshall Bowers committed on 9/4/2025, 1:46:40 PM· committed by GitHubparent28c78d2
1 file changedLine totals unavailable