Bump simplejson from 3.19.2 to 3.19.3 in /spiffworkflow-backend (#2081)

Bumps [simplejson](https://github.com/simplejson/simplejson) from 3.19.2 to 3.19.3.
- [Release notes](https://github.com/simplejson/simplejson/releases)
- [Changelog](https://github.com/simplejson/simplejson/blob/master/CHANGES.txt)
- [Commits](simplejson/simplejson@v3.19.2...v3.19.3)

---
updated-dependencies:
- dependency-name: simplejson
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>