revert a BC breaking name change

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | yes (reverting BC break compared to 1.0 - breaking for people who already updated to latest)
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #115
| License       | MIT
| Doc PR        | -

this was - probably accidentally renamed. (the doc was never updated, no changelog entry about the break, and it was inconsistent as `cmf_core.admin_extension.publish_workflow.time_period` was not changed).

if we really want to clean up the names, we would need to define alias for the old names, and update the doc and add a changelog entry. okay to simply keep them as they where in 1.0?