These tests were supposed to check the link to vote is hidden when users
don't have permission to vote. However, they aren't testing that, since
the `visible: false` option also matches visible elements. The links are
actually considered visible since they're displayed by the browser;
there's just another element on top of them.
Using `obscured: true` instead of `visible: false` solves the issue.
However, while the `obscured` option is true when the element is hidden
by another element, it's also true when the element is not currently
visible in the browser window, so in some cases we need to scroll so the
condition is effective.
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