setup.cfg: Block redis-py 4.0.0 and 4.0.1 but not >=4.0.2 (#542, #570)

Upstream commit redis/redis-py@d2b2333
that is included with redis-py >=4.0.2 adds method Redis.sentinel_masters
by making class Redis inherit from SentinelCommands, where the related code resides.

Related to issue #542, follow-up to pull request #570
This reverts (parts of) commit ef945d6.

changelog.d/542.bugfix

@@ -0,0 +1 @@
+Block use with broken redis-py 4.0.0 and 4.0.1

changelog.d/576.misc

@@ -0,0 +1 @@
+Unblock redis-py >=4.0.2

setup.cfg

@@ -38,10 +38,10 @@ packages =
     django_redis.compressors
 install_requires =
     Django>=2.2
-    redis>=3,<4
+    redis>=3,!=4.0.0,!=4.0.1
 
 [options.extras_require]
-hiredis = redis[hiredis]>=3,<4
+hiredis = redis[hiredis]>=3,!=4.0.0,!=4.0.1
 
 [coverage:run]
 omit =