Fixing typo in documentation

[ames89]

Checklist

• Issue number for this PR: #nnn (required)
• Docs included?: yes
• Test units included?: no
• In a clean directory, yarn install, yarn test run successfully? yes

Description

I'm fixing a typo

Code sample

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Thanks for your pull request. It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

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• If you've already signed a CLA, it's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.
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[ames89]

I signed it!

[googlebot]

CLAs look good, thanks!

[googlebot]

CLAs look good, thanks!

[jamesdaniels]

Thanks for the fix 👍