Update warning message in GitHub sync documentation

[robert-inkeep]

Removed the word 'corrupting' from the warning about enabling GitHub sync.

What & why

How this was verified

Checklist

• Ran bun run check (lint, typecheck, tests) locally
• Added a changeset (bun run changeset) if this changes behavior
• Updated docs if this changes a user-facing surface
• I have read CONTRIBUTING.md and agree to license my contribution under the project's terms (CLA)

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After you open this PR

• A maintainer will review your PR. If you don't hear back within a few business days, a comment to nudge is welcome.
• When your change is accepted, this PR closes automatically — that's how it merges, and your authorship is preserved.

See CONTRIBUTING.md for details.

[github-actions]

Thanks for the contribution! A maintainer will review and merge your PR. Your commit attribution is preserved as @robert-inkeep.

What happens next:

• A maintainer will review your PR.
• If you don't hear back within a few business days, please comment here to nudge — that's the right thing to do, not annoying.
• When your change is accepted, this PR closes automatically. Don't be alarmed when it closes — that's how it merges, and your authorship is preserved.

This comment will be updated as the status changes.