`test_raise_baseexception_from_task` occasionally deadlocks

### Things to check first

- [x] I have searched the existing issues and didn't find my bug already reported there

- [x] I have checked that my bug is still present in the latest release

### AnyIO version

master (14356be497c892abf372599efe84dd27ab9c4f09)

### Python version

CPython 3.13.7

### What happened?

`test_raise_baseexception_from_task` occasionally deadlocks. a71de9075a3e73e9f518bf915ba54a69e29cb93f

### How can we reproduce the bug?

https://github.com/agronholm/anyio/pull/1012#issuecomment-3447790980