Bump celery from 4.4.4 to 5.2.2 in /crawlerx_server

Bumps [celery](https://github.com/celery/celery) from 4.4.4 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@v4.4.4...v5.2.2)

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

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

crawlerx_server/requirements.txt

@@ -8,7 +8,7 @@ attrs==19.3.0
 Automat==20.2.0
 bcrypt==3.1.7
 billiard==3.6.3.0
-celery==4.4.4
+celery==5.2.2
 certifi==2020.4.5.1
 cffi==1.14.0
 chardet==3.0.4