Update ASCII art logo

What does this Merge Request do and why?

This updates the ASCII logo to match GitLab's new logo.

Before	After

This was created using jp2a 1.1.1. The command used was something like:

jp2a --width=40 --colors gitlab/app/assets/images/gitlab_logo.png

Merge Request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• [-] Tests added for new functionality. If not, please raise Issue to follow-up.
• Documentation added/updated, if needed.
• [-] gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.