Update CHANGELOG for pg_cron v1.6.7 and v1.6.6 is not showing in latest tag v1.6.7

[Basha-EDB]

We have confirmed that the changelog.md file on the main branch contains the finalized details for version v1.6.7. However, the existing v1.6.7 tag points to an earlier commit and lacks this information. Please re-point the v1.6.7 tag to the tip of the main branch to rectify the changelog content.

[Basha-EDB]

@marcoslot - I kindly request you address the incorrect changelog associated with the v1.6.7 tag at your earliest convenience.