Fixed wrong debug command (#5596)

Author: Biki-das

content/docs/how-to-contribute.md

@@ -89,7 +89,7 @@ The core team is monitoring for pull requests. We will review your pull request
 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.
-6. If you need a debugger, run `yarn debug-test --watch TestName`, open `chrome://inspect`, and press "Inspect".
+6. If you need a debugger, run `yarn test --debug --watch TestName`, open `chrome://inspect`, and press "Inspect".
 7. Format your code with [prettier](https://github.com/prettier/prettier) (`yarn prettier`).
 8. Make sure your code lints (`yarn lint`). Tip: `yarn linc` to only check changed files.
 9. Run the [Flow](https://flowtype.org/) typechecks (`yarn flow`).