Update oauth2 git documentation
What does this MR do and why?
- These docs were changed as part of !155622 (merged) but the functionality did not actually change.
- We do not validate the username anywhere.
MR acceptance checklist
Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.
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How to set up and validate locally
docs only