chore(deps): update celery requirement from ~=4.3 to ~=4.4 (#6670)

Updates the requirements on [celery](https://github.com/celery/celery) to permit the latest version.
- [Release notes](https://github.com/celery/celery/releases)
- [Changelog](https://github.com/celery/celery/blob/master/Changelog.rst)
- [Commits](celery/celery@v4.3.0...4.4.0)

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

Author: dependabot-preview[bot]

requirements/common.txt

@@ -16,7 +16,7 @@ psycopg2-binary~=2.8.4
 SQLAlchemy-Utils~=0.36.0
 itsdangerous~=1.1
 humanize~=0.5.1
-celery~=4.3
+celery~=4.4
 redis~=3.3
 apscheduler~=3.6.3
 pillow~=6.2.1