Capybara helpers already wait for the content to show up (and we already
have a default of 10 seconds configured), so I don't think waiting more is
actually the problem in these specs.
But if we wanted to wait more, I think it's better to pass the `:wait`
option to capybara matchers, because that's a "maximum waiting value"
but we'll still proceed earlier if the content shows up.
Using the same idea, I changed the positive assertions to happen first,
because negative assertions do spend "max wait time" waiting, while
positive assertions only wait until the content shows up.