Bump redis from 3.5.2 to 3.5.3

Bumps [redis](https://github.com/andymccurdy/redis-py) from 3.5.2 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@3.5.2...3.5.3)

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

requirements.txt

@@ -23,7 +23,7 @@ pyramid==1.10.4
 pyramid-multiauth==0.9.0
 pyramid-tm==2.4
 python-dateutil==2.8.1
-redis==3.5.2
+redis==3.5.3
 requests==2.23.0
 simplejson==3.17.0
 six==1.15.0