Docker fixes

[lresende]

Docker fixes:

• Update Debian security repository for the demo-base docker image
• Use more recent TensorFlow base image as old one is unavailable

Fixes #1371

[lresende]

@kevin-bates any ideas on these build failures? do we need to update any of the jupyter infra for builds?

[luong-komorebi]

Based on the logs, there is a high chance that link-check fails because of this breaking change from pytest pytest-dev/pytest#11779 on version 8.1, which I found that the job installed

The upstream package also did not lock the dependency so that pytest version should be <8.1

Therefore, from my view:

1. In the short term, we can fix this by pre-installing pytest before this line is run

   enterprise_gateway/.github/workflows/build.yml

   Line 74 in a1f9707

   - uses: jupyterlab/maintainer-tools/.github/actions/check-links@v1

2. Long term, let's open a PR to the upstream to pin the version of pytest

[lresende]

Thank you @luong-komorebi , even though I had forced the pytest to be < 8.1 forcing install on the build file before link check seems to have resolved the issue.