chore: update docs/contributing.md with yarn constraints --fix

[dbrans]

Explanation

@Gudahtt wrote:

there is a missing step, you should run yarn constraints --fix and yarn to update package versions across the repository, and then to update the lockfile.

Unfortunately I don't think this step is documented at the moment. It was an unanticipated consequence of some recent-ish changes to the release tool and to how the monorepo is structured. We have plans to automate this step as well.

References

Changelog

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've highlighted breaking changes using the "BREAKING" category above as appropriate

[mcmire]

Thanks for adding this!