Bump celery from 4.1.0 to 5.2.2 in /src

Bumps [celery](https://github.com/celery/celery) from 4.1.0 to 5.2.2.
- [Release notes](https://github.com/celery/celery/releases)
- [Changelog](https://github.com/celery/celery/blob/master/Changelog.rst)
- [Commits](celery/celery@v4.1.0...v5.2.2)

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

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

src/requirements.txt

@@ -13,7 +13,7 @@ google-api-python-client==1.7.11
 google-auth-httplib2==0.0.3
 google-auth-oauthlib==0.4.1
 
-celery==4.1.0
+celery==5.2.2
 redis==2.10.6
 django-celery-beat==1.1.1
 django-celery-results==1.0.1