base.image.version back to parsed post 6.12.1 #12813

What this PR does / why we need it:

First PR to merge after the 6.12.1. release: https://preview.guides.gdcc.io/en/develop/developers/making-releases.html#update-the-container-base-image-version-property

Which issue(s) this PR closes:

• Closes #

Special notes for your reviewer:

Suggestions on how to test this:

Does this PR introduce a user interface change? If mockups are available, please link/include them here:

Is there a release notes update needed for this change?:

Additional documentation: