fix: use deploy key for changelog direct push [2.x]

[ManukMinasyan]

Summary

• Switches changelog workflow from peter-evans/create-pull-request to direct push using deploy key
• The deploy key is added to the repo's ruleset bypass list, allowing CI to push directly to protected branches
• No more orphaned changelog PRs that need manual merge

How it works

1. actions/checkout uses ssh-key: ${{ secrets.DEPLOY_KEY }}
2. git-auto-commit-action pushes the CHANGELOG update directly to the release branch
3. The deploy key bypasses the ruleset's PR requirement

[Copilot]

Pull request overview

Updates the GitHub Actions workflow that backports release changelog updates onto the appropriate maintenance branch (e.g., 2.x) by adjusting how the repo is checked out and how the changelog commit is labeled.

Changes:

• Adds an SSH deploy key to the actions/checkout step.
• Updates the auto-commit message to include the release tag name.