Remove aggregate failures from enable_scanning_from_configuration_spec

What does this MR do and why?

I'm seeing occasional failures with this spec, for example #416233

However I am not able to reproduce locally, and the aggregate failure block means that it is difficult to tell where the test actually failed.

This MR removes - temporarily at least - the aggregate failure block, at the very least such that the next failure shows where the failure occurs, such that the test can be fixed/hardened.

Screenshots or screen recordings

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

bundle exec bin/qa Test::Instance::All https://staging.gitlab.com qa/specs/features/ee/browser_ui/13_secure/enable_scanning_from_configuration_spec.rb

MR acceptance checklist

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