fix flaky test in casa cases show spec

[fchatterji]

What github issue is this PR for, if any?

Resolves #4894

What changed, and why?

• removed the creation and login as volunteer1, as there is already a volunteer set up at the beginning of the tests. This should fix the flakiness of the previous test
• added a test that, if the hide old cases option is not checked, all cases are displayed. I felt the previous test was incomplete, it could've worked for example only because we use 2 different volunteers.
• tried to inmprove readability of the test

How will this affect user permissions?

• Volunteer permissions: /
• Supervisor permissions: /
• Admin permissions: /

How is this tested? (please write tests!) 💖💪

ran the test 100 times locally, no failure

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[FireLemons]

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