Improve CHANGELOG.md workflow

[wozniakjan]

Proposal

The CHANGELOG.md workflow is a frequent source of conflicts in PRs that would otherwise not conflict at all. This slightly reduces the positive experience contributing to KEDA and adds minor overhead for the maintainers.

Use-Case

As a contributor, I'd appreciate fewer rebases on my open PRs during the review process.
As a maintainer, I'd find it useful to have the CHANGELOG.md file generated as part of the release process.

Is this a feature you are interested in implementing yourself?

Yes

Anything else?

No response