Fix wrong `inverse_of` in `vulnerability_state_transitions` association

What does this MR do and why?

The association was introduced by !93135 (merged) on 2022-08-08 and I noticed it by chance since flaky tests count skyrocketed since this day!

This was actually reported by an external contributor at !93135 (diffs, comment 1087409806)

Screenshots or screen recordings

You can see the increase in flaky tests at https://app.periscopedata.com/app/gitlab/888968/EP---Flaky-tests?widget=12187306&udv=1474231 (internal link).

How to set up and validate locally

Without the change

• Run bin/rspec rspec './spec/requests/api/debian_project_packages_spec.rb[1:2:1:1:2:1:2]' -> the spec fails
• Run RETRIES=2 bin/rspec rspec './spec/requests/api/debian_project_packages_spec.rb[1:2:1:1:2:1:2]' -> the spec fails
• Run RETRIES=3 bin/rspec rspec './spec/requests/api/debian_project_packages_spec.rb[1:2:1:1:2:1:2]' -> the spec passes (I don't know why!)

With the change

• Run bin/rspec rspec './spec/requests/api/debian_project_packages_spec.rb[1:2:1:1:2:1:2]' -> the spec passes

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.