Implement the ability to Delete a Branch rule

Description

As part of the MVC for organizing rules based on branches, we need to implement the ability to delete a branch rule.

Scope

The scope of this issue includes:

• Delete branch rule (FE)

Implementation plan

issue	note
Branch rules MVC: Implement frontend skeleton (#362205 - closed)
Implement the ability to add branch Protections (#362212 - closed)
Implement the ability to add Merge Request appr... (#362214 - closed)
Branch rules MVC: Add GraphQL endpoint to delet... (#362219 - closed)
Branch rules MVC: List branch rules under Repos... (#362217 - closed)	⚠ blocked by #362219 (closed)
Implement the ability to Delete a Branch rule (#362218 - closed)	👈 this issue (⚠ blocked by #362219 (closed))

Mockups

• When "Delete" clicked, display modal
  • title: Delete branch rule?
  • body: Are you sure you want to delete this branch rule? This action cannot be undone.
  • destructive primary: Delete branch rule
  • secondary: Cancel
• Upon deletion the user is redirected to list of branch rules in "Settings > Repository"

Branch rule with delete button	Delete modal