fix: typo in legacy docs

[jeffqg]

Rewrite uspported -> supported.

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Fixes #2036 🦕

[conventional-commit-lint-gcf]

🤖 I detect that the PR title and the commit message differ and there's only one commit. To use the PR title for the commit history, you can use Github's automerge feature with squashing, or use automerge label. Good luck human!

-- conventional-commit-lint bot
https://conventionalcommits.org/

[chalmerlowe]

Let's have Kokoro do its thing and see if we can get this approved.

[chalmerlowe]

LGTM

[chalmerlowe]

@jeffqg

Thank you very much for submitting this fix. I appreciate the help.
If you are interested in working on another task, I would be happy to do what I can to facilitate.

Have a great day!

[jeffqg]

Thanks! I'm starting to use this API, so I'll try to address any issues I come across.