clarify that the GitHub authentication plugin is already enabled

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

Author: themr0c

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

@@ -53,7 +53,8 @@ Enter the GitHub host domain: `github.com`.
 `AUTHENTICATION_GITHUB_ORGANIZATION`::
 Enter your GitHub organization name, such as `__<your_github_organization_name>__`.
 
-. Enable the `backstage-plugin-catalog-backend-module-github-org` plugin.
+. Enable the GitHub organization provisioning plugin (`backstage-plugin-catalog-backend-module-github-org`).
+This plugin ingests GitHub users and groups to the {product-short} software catalog.
 +
 .`dynamic-plugins.yaml` file fragment
 [code,yaml]
@@ -62,6 +63,8 @@ plugins:
   - package: './dynamic-plugins/dist/backstage-plugin-catalog-backend-module-github-org'
     disabled: false
 ----
++
+The GitHub authentication plugin (`auth-backend-module-github-provider`) is already enabled by default.
 
 . To provision GitHub users and groups to the {product-short} software catalog, add the `catalog.providers.githubOrg` section to your custom {product-short} `{my-app-config-file}` configuration file:
 +