Bump wp-cli/core-command from 2.1.19 to 2.1.20

Bumps [wp-cli/core-command](https://github.com/wp-cli/core-command) from 2.1.19 to 2.1.20.
- [Release notes](https://github.com/wp-cli/core-command/releases)
- [Commits](wp-cli/core-command@v2.1.19...v2.1.20)

---
updated-dependencies:
- dependency-name: wp-cli/core-command
  dependency-version: 2.1.20
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]