Update dockerfile packages

[sjberman]

Update packages for CVEs. Also removed unnecessary library from UBI build.

Checklist

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• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Release notes

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please add a brief note that summarizes the change.

[Copilot]

Pull request overview

This PR updates Dockerfile configurations to improve package security and maintenance by ensuring Alpine Linux packages are kept up-to-date and removing unnecessary dependencies from UBI builds.

Key changes:

• Added package update and upgrade step to Alpine-based NGINX OSS Dockerfile
• Removed unnecessary shadow-utils installation and cleanup from NGINX Plus UBI Dockerfile
• Updated comment consistency across Dockerfiles

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
build/Dockerfile.nginx	Adds apk update && apk upgrade to keep Alpine packages current
build/ubi/Dockerfile.nginxplus	Removes shadow-utils package installation and cleanup since useradd is available in base image
build/ubi/Dockerfile.nginx	Updates comment to remove redundant context

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.03%. Comparing base (f536ed9) to head (671b300).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4448   +/-   ##
=======================================
  Coverage   86.03%   86.03%           
=======================================
  Files         132      132           
  Lines       14382    14382           
  Branches       35       35           
=======================================
+ Hits        12373    12374    +1     
+ Misses       1794     1793    -1     
  Partials      215      215           

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