Retry scan policy mutation if it fails in test due to race condition

What does this MR do and why?

If we try to create a scan execution policy before project authorization is updated the mutation fails. See #413667 (closed)

In this MR we wait 5 seconds for project authorization to complete and then try again. We re-raise the mutation failure error after 3 attempts.

This should also fix #414503 (closed)

How to set up and validate locally

From the qa directory:

bundle install
export WEBDRIVER_HEADLESS=false # If you'd like to watch the test in action
export QA_GITLAB_URL="http://gdk.test:3000" # Only needed if GDK is not running on http://127.0.0.1:3000
bundle exec rspec qa/specs/features/ee/browser_ui/10_govern/scan_result_policy_vulnerabilities_spec.rb

MR acceptance checklist

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