Fix Duplicate header issues

• Upgrade to actions/checkout@v4
• Disable persist-credentials
• Enhance error messages

Full Changelog: 2.1.0...2.1.3

2.1.0

Add force push sync as parameter

2.0.0

Create main.yml

1.0.1

Fixed the versioning pattern in the docs

V1.0.0

This is the first working version of my gitlab synch action.

Full Changelog: https://github.com/keninkujovic/gitlab-synch/commits/1.0.0