[E2E] PROMOTE TO BLOCKING: on_demand_dast_spec.rb

What does this MR do?

Promotes the following e2e tests to the blocking bucket:

1. Secure On Demand DAST when a scan is ran populates On Demand scan history and vulnerability report | Testcase | Spec metrics

This MR was created based on data from reliable e2e test report: #479689 (closed)

(This MR was automatically generated by gitlab_quality-test_tooling at 2024-08-19 02:05:40 UTC)