Drop aiounittest test dependency (broken on Python 3.14) #916
Description
aiounittest doesn't support 3.14 and looks like it won't anytime soon (kwarunek/aiounittest#28, last release was 2022), which means twilio's test suite can't be built anymore
Everything aiounittest does has been in the stdlib since Python 3.8 via unittest.IsolatedAsyncioTestCase, so it should be a straightforward swap.