pin trio to <0.25.0 due to breaking changes

[axiomiety]

0.25.0 causes some tests to fail - c.f. release notes

[trio-bot]

Hey @axiomiety, it looks like that was the first time we merged one of your PRs! Thanks so much! 🎉 🎂

If you want to keep contributing, we'd love to have you. So, I just sent you an invitation to join the python-trio organization on Github! If you accept, then here's what will happen:

• Github will automatically subscribe you to notifications on all our repositories. (But you can unsubscribe again if you don't want the spam.)

• You'll be able to help us manage issues (add labels, close them, etc.)

• You'll be able to review and merge other people's pull requests

• You'll get a [member] badge next to your name when participating in the Trio repos, and you'll have the option of adding your name to our member's page and putting our icon on your Github profile (details)

If you want to read more, here's the relevant section in our contributing guide.

Alternatively, you're free to decline or ignore the invitation. You'll still be able to contribute as much or as little as you like, and I won't hassle you about joining again. But if you ever change your mind, just let us know and we'll send another invitation. We'd love to have you, but more importantly we want you to do whatever's best for you.

If you have any questions, well... I am just a humble Python script, so I probably can't help. But please do post a comment here, or in our chat, or on our forum, whatever's easiest, and someone will help you out!