Condense contributors and authors fields in release notes

Currently, the contributors field is not shown at all in the final release notes. This makes it both confusing and pointless.

> [8:04 PM]cart: I disagree. User attention is limited and credit is a valuable resource that is watered down if we hand it out too readily. Imo the venn diagram of "authors" and "people who deserve to be listed" is a circle. If you deserve to be listed, you are an author. If you are an author, you deserve to be listed.
> [8:05 PM]
Alice 🌹: That's fine by me, but we should remove / alter the contributors field to make that more clear
> [8:06 PM]cart: We already sort authors by size of their contribution. I don't think we need categories here, and it increases the "informational noise" to introduce them.

No files or tests are named. Start by locating how contributors and authors are rendered in the release notes, then clarify whether contributors should be removed or combined with authors; done means the final release notes present a settled, non-confusing attribution format.

Written by the indexing model from the issue text.