fix: False positive warning about MessageChannel

[eps1lon]

What:
Closes #521

Why:

Warning was a false positive

How:

Correctly translate

warningWithoutStack(
          typeof MessageChannel !== 'undefined',
          'This browser does not have a MessageChannel implementation, ' +
            'so enqueuing tasks via await act(async () => ...) will fail. ' +
            'Please file an issue at https://github.com/facebook/react/issues ' +
            'if you encounter this warning.',
        );

warningWithoutStack (like warning) works different than console.error and is very confusing (which is also why react is getting rid of it)

Checklist:
check an item, place an "x" in the box like so: "- [x] Documentation" -->

• [ ] Documentation added to the
  docs site
• Tests: Tested with mui/material-ui@9e6a029 which should report green in https://app.circleci.com/jobs/github/mui-org/material-ui/124966
• [ ] Typescript definitions updated
• Ready to be merged
  

[kentcdodds]

Thank you!

[kentcdodds]

🎉 This PR is included in version 9.3.2 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀