Custom Content Types: sharing buttons displayed in shortcode

Steps to reproduce:
1. Activate the module
2. Go to Settings > Writing and enable the Portfolio post type
3. Create a new project within the Portfolio post type, and publish it
4. In one of your pages, add the `[portfolio]` shortcode
5. In Settings > Sharing, enable sharing buttons for Projects
6. Notice as the sharing buttons appear under each project listed with the shortcode.

Reproduce the issue through the Portfolio settings, the [portfolio] shortcode, and Sharing settings described above. Trace the shortcode's project output and sharing-button handling; done means the unintended sharing buttons no longer appear under projects rendered by the shortcode.

Written by the indexing model from the issue text.