Fix test_add_sku_with_expiry_date_in_past flakey test in iqe

https://ibutsu.insights.corp.redhat.com/project/3915c900-85fc-1222-833c-10d51af56f2e/results/0d461743-13e1-4992-a4d3-fffcbc10c6f5

Note that the function we were using to create expired subs in a pre-prod environment was updated to disallow expired subs; they may or may not re-enable this functionality in pre-prod. Slack thread: https://redhat-internal.slack.com/archives/C069WBC96N9/p1738768315953719 ; so we should move this test out of iqe.

Acceptance Criteria

• Find out how often this fails and if it's still flakey
• Since this hasn't failed recently, but required functionality that doesn't exist anymore, how is it passing?

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