docker: building with Apex (PR2455)

[Borda]

Before submitting

• [x] Was this discussed/approved via a Github issue? (no need for typos and docs improvements)
• [x] Did you read the contributor guideline, Pull Request section?
• [x] Did you make sure to update the docs?
• [x] Did you write any new necessary tests?

What does this PR do?

Apex is needed for some of our notebooks ref: https://github.com/NVIDIA/apex#linux

• [ ] validate docker build with Apex
• [ ] publish updated dockers to be used in CI
• [ ] validate ipynb with Apex -> rm this ipynb from ignore

PR review

Anyone in the community is free to review the PR once the tests have passed. If we didn't discuss your PR in Github issues there's a high chance it will not be merged.

Did you have fun?

Make sure you had fun coding 🙃