Docs: Update CI documentation for shared runner settings

doc/ci/runners/README.md

@@ -116,7 +116,7 @@ You can also enable shared runners for individual projects.
 To enable shared runners:
 
 1. Go to the project's **Settings > CI/CD** and expand the **Runners** section.
-1. Click **Allow shared runners**.
+1. Select **Enable shared runners for this project**.
 
 #### Disable shared runners
 
@@ -126,7 +126,12 @@ You must have Owner permissions for the project or group.
 To disable shared runners for a project:
 
 1. Go to the project's **Settings > CI/CD** and expand the **Runners** section.
-1. In the **Shared runners** area, click **Disable shared runners**.
+1. In the **Shared runners** area, select **Enable shared runners for this project** so the toggle is grayed-out.
+
+Shared runners are automatically disabled for a project:
+
+- If the shared runners setting for the parent group is disabled, and
+- If overriding this setting is not permitted at the project level.
 
 To disable shared runners for a group: