verify_release: Fix issue with draft releases no showing up

[jku]

I think at some point I made the verify_release use "draft:true" when uploading the draft release, instead of modifying the name.
This was a mistake as already documented by lukas in #1933:

It would be nice if we could set the release as draft at first, but that has the same caveat, i.e. it requires a token and special knowledge to download the assets.

so what happens is that while the release is a draft ./verify_release -- skip-pypi does not notice that a new GitHub release exists:

./verify_release --skip-pypi
* Built release 3.0.0
* WARNING: GitHub latest version is 2.1.0
* ERROR: GitHub artifacts do not match built release

Easiest fix would be to revert using "draft:true".

[jku]

the bug is part of this commit:
707dc49 (note both draft:true and the name changes)