Bump celery from 4.4.1 to 4.4.2 (#323)

Bumps [celery](https://github.com/celery/celery) from 4.4.1 to 4.4.2.
- [Release notes](https://github.com/celery/celery/releases)
- [Changelog](https://github.com/celery/celery/blob/master/Changelog.rst)
- [Commits](celery/celery@4.4.1...4.4.2)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>
Co-authored-by: Mariatta <Mariatta@users.noreply.github.com>

Author: dependabot-preview[bot]

requirements.txt

@@ -3,5 +3,5 @@ aiohttp==3.6.2
 gidgethub==3.3.0
 cachetools==4.0.0
 redis==3.4.1
-celery==4.4.1
+celery==4.4.2
 sentry-sdk==0.14.2