Bump serve-static and browser-sync in /guide

Bumps [serve-static](https://github.com/expressjs/serve-static) and [browser-sync](https://github.com/BrowserSync/browser-sync). These dependencies needed to be updated together.

Updates `serve-static` from 1.13.2 to 1.16.2
- [Release notes](https://github.com/expressjs/serve-static/releases)
- [Changelog](https://github.com/expressjs/serve-static/blob/v1.16.2/HISTORY.md)
- [Commits](expressjs/serve-static@v1.13.2...v1.16.2)

Updates `browser-sync` from 3.0.2 to 3.0.3
- [Release notes](https://github.com/BrowserSync/browser-sync/releases)
- [Changelog](https://github.com/BrowserSync/browser-sync/blob/master/changelog.js)
- [Commits](BrowserSync/browser-sync@v3.0.2...v3.0.3)

---
updated-dependencies:
- dependency-name: serve-static
  dependency-type: indirect
- dependency-name: browser-sync
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>