Drop react-is dependency in styled-components example (#27527)
Drop react-is dependency in styled-components example (#27527)

`react-is` dependency was [dropped](https://github.com/styled-components/styled-components/commit/8165cbe994f6f749236244f6f7017c2f0b9afcfe) as part of `styled-components@v5`.

(I don't know which checkbox to check)

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes

JeromeFitz/next.js,zeit/next.js,azukaru/next.js,JeromeFitz/next.js,flybayer/next.js,azukaru/next.js,flybayer/next.js,azukaru/next.js,azukaru/next.js,zeit/next.js,JeromeFitz/next.js,zeit/next.js,JeromeFitz/next.js,flybayer/next.js,flybayer/next.js