[Rules] Update Redirect admin area reqs to HTTPS example (#17814)

Fix target URL.

Author: pedrosousa

src/content/docs/rules/url-forwarding/examples/redirect-admin-https.mdx

@@ -23,7 +23,7 @@ This example single redirect for zone `example.com` will redirect requests for t
 
 **Then**
 
-- **Target URL**: `https://store.example.com/${1}`
+- **Target URL**: `https://store.example.com/admin${1}`
 - **Status code:** _301_
 - **Preserve query string:** Enabled