Upgrade redis-store and redis-activesupport

Now that the upstream bug is fixed and we don't use redis-store
as our cache store anymore, this should be safe to upgrade.

We need to keep this because we still use redis-store for our
session store.

Gemfile.lock

@@ -803,8 +803,8 @@ GEM
       actionpack (>= 4.0, < 7)
       redis-rack (>= 1, < 3)
       redis-store (>= 1.1.0, < 2)
-    redis-activesupport (5.0.7)
-      activesupport (>= 3, < 6)
+    redis-activesupport (5.2.0)
+      activesupport (>= 3, < 7)
       redis-store (>= 1.3, < 2)
     redis-namespace (1.6.0)
       redis (>= 3.0.4)
@@ -815,8 +815,8 @@ GEM
       redis-actionpack (>= 5.0, < 6)
       redis-activesupport (>= 5.0, < 6)
       redis-store (>= 1.2, < 2)
-    redis-store (1.6.0)
-      redis (>= 2.2, < 5)
+    redis-store (1.8.1)
+      redis (>= 4, < 5)
     regexp_parser (1.5.1)
     regexp_property_values (0.3.4)
     representable (3.0.4)