Remove scripts/prepare_release_notes.sh

### What

We have a script to convert RST release notes into markdown so that they can go into the release notes.

There are other tools to do this like pandoc
We could try just having markdown files in our repo

I think in the end we should be able to remove the script.

### Acceptance Criteria (DoD)

scripts/prepare_release_notes.sh removed and replaced with less code.

### How

_No response_