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To delete a layout forcefully after publishing, navigate to Static Resources.
After publishing a layout, a static resource for that layout is created following name convention like
layout__[layout_api_name]. Locate the specific static resource and delete it.
After deleting this static resource, you can go on the layout manager and delete the specific layout without the earlier error.
Steps to Delete a Published List View:
Note: Follow the same steps as above to delete a published list view, as well.