Merge branch 'eread/clarify-secrets-file' into 'master'

Clarify what secrets file is for

See merge request gitlab-org/gitlab!58962

doc/administration/gitaly/praefect.md

@@ -89,7 +89,7 @@ with secure tokens as you complete the setup process.
 We note in the instructions below where these secrets are required.
 
 NOTE:
-Omnibus GitLab installations can use `gitlab-secrets.json`.
+Omnibus GitLab installations can use `gitlab-secrets.json` for `GITLAB_SHELL_SECRET_TOKEN`.
 
 ### PostgreSQL