Bump wp-cli/shell-command from 2.0.15 to 2.0.16

Bumps [wp-cli/shell-command](https://github.com/wp-cli/shell-command) from 2.0.15 to 2.0.16.
- [Release notes](https://github.com/wp-cli/shell-command/releases)
- [Commits](wp-cli/shell-command@v2.0.15...v2.0.16)

---
updated-dependencies:
- dependency-name: wp-cli/shell-command
  dependency-version: 2.0.16
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]