docs: Remove REFERENCE.md from table of contents

Author: chrisburr

mkdocs.yml

@@ -109,7 +109,6 @@ nav:
       - Settings and Preferences: admin/reference/settings-and-preferences.md
       - Environment variables: admin/reference/env_variables.md
       - Charts values: admin/reference/values.md
-      - REFERENCE.md
       - RUN_PROD.md
       - SSO.md