chore: delete release-drafter

[yoshinorin]

What does it do?

Now GitHub can generate release note from PRs.
IMHO we do not need the release-drafter.

https://docs.github.com/en/repositories/releasing-projects-on-github/automatically-generated-release-notes

Thank you :)

Pull request tasks

• Add test cases for the changes.
• Passed the CI test.

[github-actions]

How to test

git clone -b drop/release-drafter https://github.com/yoshinorin/hexo.git
cd hexo
npm install
npm test

[coveralls]

Coverage decreased (-0.04%) to 98.337% when pulling 49b7a17 on yoshinorin:drop/release-drafter into 354f1f1 on hexojs:master.

[SukkaW]

LGTM! And this feature (provided by GitHub) eliminates the need of updating existing draft releases every time a commit is pushed!