chore: bump nginx plus and njs versions

[dekobon]

Proposed changes

Update NGINX Plus and njs versions.

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[github-actions]

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[Copilot]

Pull Request Overview

This PR updates the base Dockerfiles to use newer NGINX Plus and njs versions.

• Bump NGINX_VERSION from 32 to 34
• Bump NJS_VERSION from 0.8.4 to 0.9.0

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Dockerfile.plus	Updated NGINX_VERSION and NJS_VERSION envs
Dockerfile.buildkit.plus	Updated NGINX_VERSION and NJS_VERSION envs

[dekobon]

I have hereby read the F5 CLA and agree to its terms

[alessfg]

recheck