RHIDP-4248 Finish removing authentication sections from the Getting started guide

Signed-off-by: Fabrice Flore-Thébault <[email protected]>

Author: themr0c

modules/authentication/proc-enabling-authentication-with-github.adoc

@@ -55,9 +55,6 @@ TIP: If you plan to make changes using the GitHub API, ensure that `Read and wri
 +
 `AUTH_GITHUB_APP_ID`:: Enter the saved **App ID**.
 `AUTH_GITHUB_CLIENT_ID`:: Enter the saved **Client ID**.
-+
-Optional: enter additional secrets. The additional secrets are not required for authentication, but for further integration with GitHub, including:
-+
 `GITHUB_HOST_DOMAIN`:: Enter your GitHub host domain: `pass:c[https://github.com]` unless you are using GitHub Enterprise.
 `GITHUB_ORGANIZATION`:: Enter your GitHub organization name, such as `__<your_github_organization_name>__'.
 `GITHUB_ORG_URL`:: Enter `$GITHUB_HOST_DOMAIN/$GITHUB_ORGANIZATION`.