Bump celery from 3.1.26.post2 to 5.2.2 in /src

Bumps [celery](https://github.com/celery/celery) from 3.1.26.post2 to 5.2.2.
- [Release notes](https://github.com/celery/celery/releases)
- [Changelog](https://github.com/celery/celery/blob/master/Changelog.rst)
- [Commits](https://github.com/celery/celery/commits/v5.2.2)

---
updated-dependencies:
- dependency-name: celery
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

src/requirements.txt

@@ -3,7 +3,7 @@ anyjson==0.3.3
 asgiref==3.2.7
 autopep8==1.5.2
 billiard==3.3.0.23
-celery==3.1.26.post2
+celery==5.2.2
 Django==3.1.12
 django-celery==3.3.1
 django-contrib-comments==1.9.2