Add changelog entry for tenup-content-connect-update-relationships-order action

[s3rgiosan]

Description of the Change

Adds a missing changelog entry for the tenup-content-connect-update-relationships-order action introduced in #123. The entry is added under the ## [2.0.0] → ### Added section:

tenup-content-connect-update-relationships-order action for developers to run logic after relationship order is saved, firing for post-to-post, post-to-user, and user-to-post relationships (props @ocean90 via #123).

How to test the Change

1. Open CHANGELOG.md.
2. Confirm the entry appears under ## [2.0.0] → ### Added.

Changelog Entry

Added - tenup-content-connect-update-relationships-order action for developers.

Credits

Props @ocean90

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added Critical Flows, Test Cases, and/or End-to-End Tests to cover my change.
• All new and existing tests pass.