chore(alibi-explain): Deprecate GPU-related files, improve README, resolve CVEs

[vtaskow]

What

Summary of changes

• Updated Dockerfile to resolve a CVE in pip/setuptools
• Update python deps to resolve CVEs
• Remove GPU-related make commands, rename files to deprecated
• Improve README for running explainers locally

Checklist

• Added/updated unit tests
• Added/updated documentation
• Checked for typos in variable names, comments, etc.
• Added licences for new files

Testing

• All unit tests are passing
• ⚠️ All makefile commands for running explainers are passing WITH THE EXCEPTION of the Tree Shap ones