Bump axios from 0.19.2 to 0.21.4 in /examples/webserver

Bumps [axios](https://github.com/axios/axios) from 0.19.2 to 0.21.4.
- [Release notes](https://github.com/axios/axios/releases)
- [Changelog](https://github.com/axios/axios/blob/v0.21.4/CHANGELOG.md)
- [Commits](axios/axios@v0.19.2...v0.21.4)

---
updated-dependencies:
- dependency-name: axios
  dependency-type: indirect
...

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Author: dependabot[bot]