Wrong layout of the Newest Users block on challenge pages

Problem/Motivation

The wrong layout of the Newest Users block on the challenge pages.

Steps to reproduce

1. Enable Social Challenge and Social Collaboration modules.
3. Create a challenge page.
5. Add the user inside the Editor tab.
7. Save and check the block on the left sidebar.

Proposed resolution

Improve the layout of the Newest Users block on the challenge pages.

Remaining tasks

N/A

User interface changes

The Newest Users block has the correct layout on the challenge pages.

API changes

N/A

Data model changes

N/A