Bump celery from 4.3.0rc1 to 4.3.0rc2 in /requirements
Bump celery from 4.3.0rc1 to 4.3.0rc2 in /requirements

Bumps [celery](https://github.com/celery/celery) from 4.3.0rc1 to 4.3.0rc2.
- [Release notes](https://github.com/celery/celery/releases)
- [Changelog](https://github.com/celery/celery/blob/master/Changelog)
- [Commits](https://github.com/celery/celery/commits)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
edmorley/treeherder,KWierso/treeherder,KWierso/treeherder,edmorley/treeherder,edmorley/treeherder,KWierso/treeherder,edmorley/treeherder,KWierso/treeherder