MNT Update behat tests to support toast messages

[sabina-talipova]

Parent issue

• ModelAdmin doesn't have toasts on error or success silverstripe-admin#1544

[GuySartorelli]

Can you please explain why you're adding this? Was it failing there consistently? Or was it just a once-off failure? If you can re-run it and it passes, we don't tend to add additional wait statements, or we'd end up with an hour long behat run.

[sabina-talipova]

The problem is that when we run the tests, they run on a small screen and the tab "Recipients" appears directly under the toast. Another option is to click on the close toast button, but this one is easier.

[GuySartorelli]

I was going to ask you to use the "I dismiss all toasts" syntax but it looks like that's not available for CMS 4. Given that, and the fact that you're just adding this the once, and it seems like that's what has been done earlier in this same feature, I'll allow it.