Bump superdesk-planning from a26947d to cebd5db in /client

Bumps [superdesk-planning](https://github.com/superdesk/superdesk-planning) from `a26947d` to `cebd5db`.
- [Release notes](https://github.com/superdesk/superdesk-planning/releases)
- [Commits](superdesk/superdesk-planning@a26947d...cebd5db)

---
updated-dependencies:
- dependency-name: superdesk-planning
  dependency-type: direct:production
...

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