fix: Remove workaround for page-specific rendering

[fsbraun]

Description

Once, https://github.com/django-cms/django-cms/pull/7924 is merged, the work-around for page-specific rendering is not needed any more. This reactivates the {% placeholder "my_placeholder" inherit %} functionality.

Fixes #410.

Requires tests to be added.

Related resources

• https://github.com/django-cms/django-cms/pull/7924

• 410

Checklist

• [x] I have opened this pull request against master
• [ ] I have added or modified the tests when changing logic
• [x] I have followed the conventional commits guidelines to add meaningful information into the changelog
• [x] I have read the contribution guidelines and I have joined #workgroup-pr-review on Slack to find a “pr review buddy” who is going to review my pull request.