Update Fulfillment group upgrade test to use `group.path` in verification

What does this MR do and why?

• Temporary workaround for failures in #345942 (closed)

• More permanent fix would be fix #345968 (closed)

Describe in detail what your merge request does and why.

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How to set up and validate locally

Run

bundle exec bin/qa Test::Instance::All https://staging.gitlab.com -qa/specs/features/ee/browser_ui/fulfillment/purchase/upgrade_group_spec.rb

MR acceptance checklist

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