ci: fix tests

- flask docu on readthedocs is no longer available
- use beta tags for autoscale runners
6 jobs for 42-replace-external-requests in 22 minutes and 12 seconds (queued for 3 seconds)
latest
Status Name Job ID Coverage
  Test
passed py3.5-min-mysql #16422
beta

00:12:16

92.0%
passed py3.5-min-postgresql #16420
beta

00:12:08

92.0%
passed py3.5-min-sqlite #16418
beta

00:22:12

91.0%
passed py3.5-pypi-mysql #16423
beta

00:11:52

92.0%
passed py3.5-pypi-postgresql #16421
beta

00:13:44

92.0%
passed py3.5-pypi-sqlite #16419
beta

00:11:22

91.0%