Replace confirm danger modal in remove project fork form

Background

As part of our effort to replace bootstrap modals, we should replace the existing haml confirm_modal with a vue component, utilising GlModal.

This issue replaces the remaining usages of the confirm_modal, with our new vuejs modal introduced in #342115 (closed).

Given the modal is used in some fairly sensitive parts of the codebase, it makes sense to migrate each instance in separate MRs, this should hopefully reduce any possible negative impacts.

TODO

This issue is specifically for the confirm danger modal located in app/views/projects/_remove_fork.html.haml

Related to #342116 (closed).