Revert 5.6.0 release commits

[sarah-witt]

Requirements for Contributing to this repository

• Fill out the template below. Any pull request that does not include enough information to be reviewed in a timely manner may be closed at the maintainers' discretion.
• The pull request must only fix one issue at the time.
• The pull request must update the test suite to demonstrate the changed functionality.
• After you create the pull request, all status checks must be pass before a maintainer reviews your contribution. For more details, please see CONTRIBUTING.

What does this PR do?

Revert 5.6.0 release commits, as the release failed

Description of the Change

Alternate Designs

Possible Drawbacks

Verification Process

Additional Notes

Release Notes

Review checklist (to be filled by reviewers)

• Feature or bug fix MUST have appropriate tests (unit, integration, etc...)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have one changelog/ label attached. If applicable it should have the backward-incompatible label attached.
• PR should not have do-not-merge/ label attached.
• If Applicable, issue must have kind/ and severity/ labels attached at least.