Use wait_for_all_requests in jira_connect/branches_spec.rb

What does this MR do and why?

Fixes flaky tests identified in #386208 (closed)

Screenshots or screen recordings

n/a

How to set up and validate locally

Run test locally

bin/rspec spec/features/jira_connect/branches_spec.rb

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #386208 (closed)