Merge branch 'docs-fix-proj-templates' into 'master'

Docs: custom project templates - fix page title

See merge request gitlab-org/gitlab-ee!6993

doc/user/admin_area/custom_project_templates.md

-## Custom project templates **[PREMIUM ONLY]**
+# Custom project templates **[PREMIUM ONLY]**
 
 > **Notes:**
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-ee/issues/6860) in [GitLab Premium](https://about.gitlab.com/pricing) 11.2