Fix spelling in react-devtools CHANGELOG.md

[morgsmccauley]

Before submitting a pull request, please make sure the following is done:

1. Fork the repository and create your branch from master.
2. Run yarn in the repository root.
3. If you've fixed a bug or added code that should be tested, add tests!
4. Ensure the test suite passes (yarn test). Tip: yarn test --watch TestName is helpful in development.
5. Run yarn test-prod to test in the production environment. It supports the same options as yarn test.
6. If you need a debugger, run yarn debug-test --watch TestName, open chrome://inspect, and press "Inspect".
7. Format your code with prettier (yarn prettier).
8. Make sure your code lints (yarn lint). Tip: yarn linc to only check changed files.
9. Run the Flow typechecks (yarn flow).
10. If you haven't already, complete the CLA.

Learn more about contributing: https://reactjs.org/docs/how-to-contribute.html

[facebook-github-bot]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. In order for us to review and merge your code, please sign up at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need the corporate CLA signed.

If you have received this in error or have any questions, please contact us at cla@fb.com. Thanks!

[sizebot]

No significant bundle size changes to report.

Generated by 🚫 dangerJS

[facebook-github-bot]

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