Remove ProjectBrowserUiTestTrait::clickWithWait()

This is a strange, old helper function in our tests. It is not really a good method -- it makes it hard to tell what you're actually clicking, and it offers very little way to understand what, exactly, you're waiting for. It also has the ability to bypass the wait, which feels for all the world like a kludge that shouldn't be there.

We have better, more explicit assertion methods now, and don't need to rely on CSS selectors as much. Mink offers us a broad API for interacting with the page, and waiting for things. Its API is far more expressive, too. Let's switch to Mink's methods, and our own custom assertions/wait helpers, instead of relying on hard-to-grok stuff like clickWithWait().