removed PGADMIN_LISTEN_PORT

[ValClarkson]

Checklist:

• [ x] Have you added an explanation of what your changes do and why you'd like them to be included?
• [ ] Have you updated or added documentation for the change, as applicable?
• [x ] Have you tested your changes on all related environments with successful results, as applicable?
  • [ x] Have you added automated tests?

Type of Changes:

• [ ] New feature
• [ ] Bug fix
• [ ] Documentation
• [ ] Testing enhancement
• [ x] Other

What is the current behavior (link to any open issues here)?

What is the new behavior (if this is a feature change)?

• [ ] Breaking change (fix or feature that would cause existing functionality to change)

removed PGADMIN_LISTEN_PORT

Other Information: Issue: [PGO-1176]