4.x SE health page and guide need to refer to the new required dependency and update the endpoints in a couple places

[tjquinno]

Environment Details

• Helidon Version: 4.0.0
• Helidon SE or Helidon MP SE
• JDK version:
• OS:
• Docker version (if applicable):

---

Problem Description

The SE health guide and pages should mention the new dependency on helidon-webserver-observe-health.

Most examples were corrected earlier, but there are a few places where the old endpoints are still used in examples.