Fix inaccurate comment for uvarint

[gammazero]

This fixes the comment to be consistent with the code, and fixes spelling.

Fixes Issue #111

[welcome[bot]]

Thank you for submitting this PR! A maintainer will be here shortly to review it. We are super grateful, but we are also overloaded! Help us by making sure that:

• The context for this PR is clear, with relevant discussion, decisions and stakeholders linked/mentioned.

• Your contribution itself is clear (code comments, self-review for the rest) and in its best form. Follow the code contribution guidelines if they apply.

Getting other community members to do a review would be great help too on complex PRs (you can ask in the chats/forums). If you are unsure about something, just leave us a comment. Next steps:

• A maintainer will triage and assign priority to this PR, commenting on any missing things and potentially assigning a reviewer for high priority items.

• The PR gets reviews, discussed and approvals as needed.

• The PR is merged by maintainers when it has been approved and comments addressed.

We currently aim to provide initial feedback/triaging within two business days. Please keep an eye on any labelling actions, as these will indicate priorities and status of your contribution. We are very grateful for your contribution!