Bump deliciousbrains/wp-background-processing from 1.3.1 to 1.4.0

Bumps [deliciousbrains/wp-background-processing](https://github.com/deliciousbrains/wp-background-processing) from 1.3.1 to 1.4.0.
- [Release notes](https://github.com/deliciousbrains/wp-background-processing/releases)
- [Commits](deliciousbrains/wp-background-processing@1.3.1...1.4.0)

---
updated-dependencies:
- dependency-name: deliciousbrains/wp-background-processing
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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