Bump redis-rack from 2.0.4 to 2.1.2 (#13512)

Bumps [redis-rack](http://redis-store.org/redis-rack) from 2.0.4 to 2.1.2.

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Gemfile.lock

@@ -500,15 +500,15 @@ GEM
       redis-store (>= 1.3, < 2)
     redis-namespace (1.7.0)
       redis (>= 3.0.4)
-    redis-rack (2.0.4)
-      rack (>= 1.5, < 3)
+    redis-rack (2.1.2)
+      rack (>= 2.0.8, < 3)
       redis-store (>= 1.2, < 2)
     redis-rails (5.0.2)
       redis-actionpack (>= 5.0, < 6)
       redis-activesupport (>= 5.0, < 6)
       redis-store (>= 1.2, < 2)
-    redis-store (1.5.0)
-      redis (>= 2.2, < 5)
+    redis-store (1.8.2)
+      redis (>= 4, < 5)
     regexp_parser (1.7.0)
     request_store (1.5.0)
       rack (>= 1.4)