Add tier badges

Add tier badges to Redis-related pages

doc/administration/redis/index.md

@@ -5,7 +5,7 @@ group: Distribution
 info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
 ---
 
-# Configuring Redis for scaling
+# Configuring Redis for scaling **(FREE SELF)**
 
 Based on your infrastructure setup and how you have installed GitLab, there are
 multiple ways to configure Redis.

doc/administration/redis/troubleshooting.md

@@ -5,7 +5,7 @@ group: Distribution
 info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
 ---
 
-# Troubleshooting Redis
+# Troubleshooting Redis **(FREE SELF)**
 
 There are a lot of moving parts that needs to be taken care carefully
 in order for the HA setup to work as expected.