In component tests, the `within` method is actually an alias to RSpec's
`be_within` matcher, which is used to test numeric ranges. That meant
the tests always passed, even when there were bugs on the page.
In order to use `within` in component tests, we have to use
`page.within`. However, that also fails, since there's no such method
for `Capybara::Node::Simple'` objects, which are used in component
tests.
So we're using `page.find` instead.
See also pull request 945 in https://github.com/github/view_component
The `sign_in(nil)` method was a bit hard to understand IMHO. After all,
in controller and system tests we don't have to specify no user is
signed in; that's the default behavior.
So we're making it the default behavior for component tests as well.
