ci: disable automated pre-releases, refer to release notes on GitHub

[daniel-mader]

Description of change

• The CHANGELOG.md does not need to be maintained any longer (due to automatically created release notes by semantic releases). We follow the suggestion by semantic-release and refer to the releases on GitHub instead.

• Automated pre-releases for beta and alpha are switched from "release on push to branch" to "triggered manually". This allows the team to collect changes and release manually to reduce the total amount of pre-release versions.
  This setup can be changed again at any time until we find a release schedule that fits well.

Links to any relevant issues

n/a

How the change has been tested

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Definition of Done checklist

Add an x to the boxes that are relevant to your changes.

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have successfully tested this change in a docker environment

[github-actions]

🎉 This PR is included in version 1.0.0-beta.5 🎉

The release is available on GitHub release

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