fix: remove has assets condition

[ReenigneArcher]

• Fixes Trying to delete all except 1 pre-release, not working #46
• Fixes Unable to cleanup releases #44
• Fixes Failed to get list of releases <- Not Found #42

I don't think this is a bug in GitHub's API, but was perhaps a bug before. zipball and tarball "assets" are in a separate key as you can see here, and probably should have never been listed under "assets".

I also don't see a valid reason why you would use "assets" count to verify if it's a release or not. You already know it's a release because it's in the releases api.

P.S. It's unfortunate, but I'm pretty sure no one from GitHub will ever read anything in their community discussions: https://github.com/orgs/community/discussions/116306

[thadguidry]

Totally agree that we should not use "assets" count for verifying. I am only the maintainer, not the original developer. In fact, I don't develop on this project, but instead allow the community to contribute and review and test.

I'll merge your changes as it does seem like these fix the original underlying bug.