Bump redis from 5.2.0 to 5.2.1 (#780)

Bumps [redis](https://github.com/redis/redis-py) from 5.2.0 to 5.2.1.
- [Release notes](https://github.com/redis/redis-py/releases)
- [Changelog](https://github.com/redis/redis-py/blob/master/CHANGES)
- [Commits](redis/redis-py@v5.2.0...v5.2.1)

---
updated-dependencies:
- dependency-name: redis
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements.txt

@@ -24,7 +24,7 @@ django-sendgrid-v5==1.2.4
 psycopg2-binary==2.9.10
 # Having problems deploying to Heroku with 1.6.3
 pylibmc==1.6.3
-redis==5.2.0
+redis==5.2.1
 rollbar==1.1.0
 
 # web server