chore(datasets): Demote `VideoDataset` to experimental datasets

[merelcht]

Description

Proposal to demote the VideoDataset, reasons:

• Several tests were already marked to be skipped/xfail: https://github.com/kedro-org/kedro-plugins/blob/main/kedro-datasets/tests/video/test_video_dataset.py
• It's currently pinned to use opencv-python~=4.5.5.64 which causes issues with newer Numpy versions (from 2.0).
• Bumping opencv to fix the numpy issue, makes several tests fail and I haven't figured out how to fix them..

[!IMPORTANT] Requires TSC vote

Checklist

• [ ] Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• [x] Updated the documentation to reflect the code changes
• [x] Added a description of this change in the relevant RELEASE.md file
• [ ] Added tests to cover my changes
• [x] Received approvals from at least half of the TSC (required for adding a new, non-experimental dataset)

[merelcht]

Is it considered a breaking change? If yes, is the next version a major one? (Though if tests are failing, I don't think it works in its current state)

Yes this is indeed a breaking change. I'll update the release notes to make it clear! The next release will now be 6.0.0.

[merelcht]

10/20 TSC approval meets the 1/2 requirement, so merging.