By default, Capybara only finds visible elements, so adding the
`visible: true` option is usually redundant.
We were using it sometimes to make it an obvious contrast with another
test using `visible: false`. However, from the user's perspective, we
don't care whether the element has been removed from the DOM or has been
hidden, so we can just test that the visible selector can't be found.
Besides, using `visible: false` means the test will also pass if the
element is present and visible. However, we want the test to fail if the
element is visible. That's why a couple of JavaScript-dependant tests
were passing even when JavaScript was disabled.
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.
