Bump superdesk-planning from ec31062 to 71c99ed in /client

Bumps [superdesk-planning](https://github.com/superdesk/superdesk-planning) from `ec31062` to `71c99ed`.
- [Release notes](https://github.com/superdesk/superdesk-planning/releases)
- [Commits](superdesk/superdesk-planning@ec31062...71c99ed)

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

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