Add Free tier to Pages docs

Add Free tier to Pages-related docs for admin.

doc/administration/pages/index.md

@@ -5,7 +5,7 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 description: 'Learn how to administer GitLab Pages.'
 ---
 
-# GitLab Pages administration
+# GitLab Pages administration **(FREE SELF)**
 
 > - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/80) in GitLab EE 8.3.
 > - Custom CNAMEs with TLS support were [introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/173) in GitLab EE 8.5.

doc/administration/pages/source.md

@@ -4,7 +4,7 @@ group: Release
 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
 ---
 
-# GitLab Pages administration for source installations
+# GitLab Pages administration for source installations **(FREE SELF)**
 
 NOTE:
 Before attempting to enable GitLab Pages, first make sure you have