Bump redis-rack from 2.1.2 to 2.1.3 (#14584)

Bumps [redis-rack](http://redis-store.org/redis-rack) from 2.1.2 to 2.1.3.

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile.lock

@@ -482,7 +482,7 @@ GEM
       redis-store (>= 1.3, < 2)
     redis-namespace (1.7.0)
       redis (>= 3.0.4)
-    redis-rack (2.1.2)
+    redis-rack (2.1.3)
       rack (>= 2.0.8, < 3)
       redis-store (>= 1.2, < 2)
     redis-rails (5.0.2)