chore(deps-dev): bump nx from 19.8.2 to 20.4.6

Bumps [nx](https://github.com/nrwl/nx/tree/HEAD/packages/nx) from 19.8.2 to 20.4.6.
- [Release notes](https://github.com/nrwl/nx/releases)
- [Commits](https://github.com/nrwl/nx/commits/20.4.6/packages/nx)

---
updated-dependencies:
- dependency-name: nx
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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