Bump serialize-javascript and workbox-build

Bumps [serialize-javascript](https://github.com/yahoo/serialize-javascript) and [workbox-build](https://github.com/googlechrome/workbox). These dependencies needed to be updated together.

Updates `serialize-javascript` from 4.0.0 to 6.0.2
- [Release notes](https://github.com/yahoo/serialize-javascript/releases)
- [Commits](yahoo/serialize-javascript@v4.0.0...v6.0.2)

Updates `workbox-build` from 7.0.0 to 7.3.0
- [Release notes](https://github.com/googlechrome/workbox/releases)
- [Commits](GoogleChrome/workbox@v7.0.0...v7.3.0)

---
updated-dependencies:
- dependency-name: serialize-javascript
  dependency-type: indirect
- dependency-name: workbox-build
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]