Add Pivotal Tracker logo

Purpose

We are adding Pivotal Tracker integration logos, as per gitlab#367591 (closed), followed the spreadsheets.

Approval status:

"Approved as long as their brand guidelines are followed. (No account named for them on file. If there is an agreement in place, legal will need to review it before proceeding.)"

Screenshots

Checklist

For a new icon and/or illustration:

• Link to related design issue:
• If this adds an icon ensure that it follows the new icon checklists.
• If this adds an illustration ensure that it follows the new illustration checklists.

For third-party trademarks:

• If this adds or updates an icon or illustration that includes a third-party trademark, ensure that it follows the process for adding third-party trademarks to GitLab.