Change icon and color of issue statuses in related issues and epic issues

• To keep the list of related issues and epic issues consistent with https://gitlab.com/gitlab-org/gitlab-ce/issues/33926, the issue statuses should be configured as:
• Open:
  • Color: $green-500
  • Icon: issue-open
• Closed:
  • Color: $blue-500
  • Icon: issue-close

• Note that this applies to the issues in epics as well as the issues in related issues.