Should not use green for feedback when no tests where executed

[mkarnicki]

Hi and thanks for your sweet plugin :)

How to reproduce:

1. Write a test
2. Forget to annotate with /** @test */ and don't use test_ in name.
3. Use the plugin to run it on a single test.

What happens:

1. Plugin runs phpunit with --filter on the focused test.
2. It shows a green pop-up (reminding the one when tests pass) that 'no tests were run'

What should happen:

1. The plugin should probably use yellow color, just like phpunit, to make it clear that no tests where run. Using green can confuse the developer the test has run and passed. Sure, the box says no tests run, but it's way too easy to confuse passing with 'no tests run' right now. This is why phpunit uses a yellow background warning in the output "No tests executed!"

Thanks 💪