@next GitHub release date does not advance

[ddbeck]

The https://github.com/web-platform-dx/web-features/releases/tag/next release is continuously updated with the latest (test-passing) commit. However, because it updates an existing tag instead of creating a new one, the release date never advances on GitHub, so it sorts oddly, to the fixed time we created the workflow, well before v2.0.0.

We ought to use some steps as described in softprops/action-gh-release#171 (comment) to automatically advance the tag date on each publish for the @next release.

[ddbeck]

While I'm at it, I think it'd be a good idea to stop using softprops/action-gh-release itself. The latest update #2131 had me dig into what was being released and why (the release notes were vague). That led me to find that the maintainership of the action has been handed over to someone else, but there's no documentation about it. Seems… iffy.

I think we can do the same with the gh CLI, something like:

run: >
  gh release create
  --verify-tag
  --title 'web-features@next'
  --notes 'This is a continuously-updated prerelease generated from `main` (currently at ${{ steps.timestamp_and_hash.outputs.SHORT_HASH }}).'
  --prerelease
  --latest=false
  next
  <artifact paths go here>

(Of course, we'll have to delete and recreate the next tag in the step preceding this one.)