Update mainline NGINX to 1.25.3

[abscondment]

Proposed changes

Updating mainline to NGINX 1.25.3, which includes this change:

Changes with nginx 1.25.3 24 Oct 2023

*) Change: improved detection of misbehaving clients when using HTTP/2.

Also updates njs to 0.8.2, which is required for the NGINX change to build.

Related to #166

Checklist

Before creating a PR, run through this checklist and mark each as complete:

• I have read the CONTRIBUTING document
• I have run ./update.sh and ensured all entrypoint/Dockerfile template changes have been applied to the relevant image entrypoint scripts & Dockerfiles
• I have tested that the NGINX Unprivileged Docker images build and run correctly on all supported architectures on an unprivileged environment (check out the README for more details)
• I have updated any relevant documentation (README)

[abscondment]

I couldn't find any specific guidance for testing all of the README.md#architectures, so I wrote this up: https://gist.github.com/abscondment/e12fd25b9ada4d4445f8b2e286e5d6cc

All mainline images passed for all listed architectures using this script.

[alessfg]

Thanks for the PR, and sorry it took so long to merge! I have been offline for the past couple weeks.

You are right that there is no real guidance on how to test changes. I have my own little script not unlike yours, and it's on my todo list to create an "offline" GH actions workflow that can be easily tested locally using act or other similar tools. For the time being though, I might combine both our scripts and ask users to use that for tests!

[alessfg]

Opened an issue to track improving the local testing docs (#173)!