Bump redis from 3.4.1 to 3.5.3 (#339)

Bumps [redis](https://github.com/andymccurdy/redis-py) from 3.4.1 to 3.5.3.
- [Release notes](https://github.com/andymccurdy/redis-py/releases)
- [Changelog](https://github.com/andymccurdy/redis-py/blob/master/CHANGES)
- [Commits](redis/redis-py@3.4.1...3.5.3)

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

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

Author: dependabot-preview[bot]

requirements.txt

@@ -2,6 +2,6 @@ cherry_picker==1.3.2
 aiohttp==3.6.2
 gidgethub==4.1.0
 cachetools==4.1.0
-redis==3.4.1
+redis==3.5.3
 celery==4.4.3
 sentry-sdk==0.14.4