Fixed async redis code snippet (#11267)

Author: antonpirker

docs/platforms/python/integrations/redis/index.mdx

@@ -59,11 +59,11 @@ import redis.asyncio as redis
 
 async def main():
     sentry_sdk.init(...)  # same as above
-    rc = RedisCluster(host='localhost', port=16379)
+    r = redis.Redis(host='localhost', port=6379)
 
     with sentry_sdk.start_transaction(name="testing_sentry"):
-        rc.set("foo", "bar")
-        rc.get("foo")
+        await r.set("foo", "bar")
+        await r.get("foo")
 
 asyncio.run(main())
 ```