fix protected branches sane defaults feature on EE

What does this MR do?

• Fixes the Protected branch form should have sane defaults for dropdowns as it didn't quite work on EE
• Solves the conflicts for the protected branches spec although one spec is missing

Screenshots

Does this MR meet the acceptance criteria?

• Review
  • Has been reviewed by Frontend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?