Fix regressions in the design of the project statistics bar.

## What does this MR do?

Improves the design of the empty Changelog, Contribution guide, and License items in the project statistics bar.

## Are there points in the code the reviewer needs to double check?

Don't think so, maybe that the `project-stats` class isn't used anywhere else (a grep suggests it's not)

## Why was this MR needed?

Because the empty state of the repository didn't look as good anymore.

## What are the relevant issue numbers?
#18734

## Screenshots (if relevant)

Before:

![Screen_Shot_2016-06-16_at_12.15.22_PM](/uploads/a5c27d696af186346a2298071c90ba2d/Screen_Shot_2016-06-16_at_12.15.22_PM.png)

After:

![Screen_Shot_2016-06-16_at_12.59.38_PM](/uploads/8719d3ee507affd4ce7ea479a5422908/Screen_Shot_2016-06-16_at_12.59.38_PM.png)

See merge request !4717