Update AppProtect WAF doc references in NIC docs

[vepatel]

Describe the bug

• Update AppProtect WAF doc references for v4
  On https://docs.nginx.com/nginx-ingress-controller/troubleshooting/troubleshooting-app-protect-waf
  This was a pointer to - https://docs.nginx.com/nginx-app-protect-waf/configuration/#external-references which now returns a page not found.

[github-actions]

Hi @vepatel thanks for reporting!

Be sure to check out the docs and the Contributing Guidelines while you wait for a human to take a look at this 🙂

Cheers!

[ADubhlaoich]

Notes for self:

• This document can probably moved into the integrations subsection
• There's likely other broken links of this nature that need to be fixed

[ADubhlaoich]

Put up a draft PR I will be pushing changes into as I go. There's a lot of problems with links in the documentation I will address: I'm also going to fix some low hanging fruit with the content while I'm at it.