Breaking: Remove obsolete sidebar headline

Description

The sidebar headline does not deliver any benefit. The user has the option to use the title of the content element to add a headline to the sidebar if necessary, in general this has no real use case since only the headlines of the widgets are relevant.

Change

https://github.com/TYPO3GmbH/blog/commit/7fac00acf6209777b6e73598159aea979da0e2ae