testing/py3-fastapi: disable parallel testing and upgrade to 0.100.1
Full logs of some of the failed parallel tests here: https://paste.sr.ht/blob/0adc6f4b615e667c25b6fb4a2b8bd4b1e6dab600
Full logs of some of the failed parallel tests here: https://paste.sr.ht/blob/0adc6f4b615e667c25b6fb4a2b8bd4b1e6dab600