Replace the delete SSH confirmation dialog with a Pajamas Modal

Summary

The current delete SSH key confirmation uses a browser dialog. 🙀

This dialog isn't inline with our design system, nor is it the best or most informative user experience:

Instances of this dialog:

• Admin/users
• Profile/settings
• Admin/credentials (when #225248 (closed) is completed)
• Group/credentials (when #225248 (closed) is completed)

Proposal

Replace the browser dialog with a Pajamas Modal confirmation dialog using GlModal.