chore: Drop EOL Node.js 18

[mertssmnoglu]

Description

Remove Node.js 18 related files and updated the versions.json

Motivation and Context

Node.js 18 has reached EOL at 30 April 2025. Minimum recommended Node.js version is 20.x.x for now.

• https://nodejs.org/en/about/previous-releases#nodejs-releases
• nodejs/Release@c1cf5e9

Types of changes

• Documentation
• Version change (Update, remove or add more Node.js versions)
• Variant change (Update, remove or add more variants, or versions of variants)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Other (none of the above)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING.md document.
• All new and existing tests passed.

[github-actions]

Created PR on the official-images repo (docker-library/official-images#19118). See https://github.com/docker-library/faq#an-images-source-changed-in-git-now-what if you are wondering when it will be available on the Docker Hub.