Bump celery from 5.1.0 to 5.1.2 (#470)

Bumps [celery](https://github.com/celery/celery) from 5.1.0 to 5.1.2.
- [Release notes](https://github.com/celery/celery/releases)
- [Changelog](https://github.com/celery/celery/blob/master/Changelog.rst)
- [Commits](celery/celery@v5.1.0...v5.1.2)

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: Łukasz Langa <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -4,6 +4,6 @@ aiohttp==3.7.4.post0
 gidgethub==5.0.1
 cachetools==4.2.2
 redis==3.5.3
-celery==5.1.0
+celery==5.1.2
 sentry-sdk==1.3.1
 click==7.1.2