software/slapos-sr-testing: fix python3 profile

It got broken in 3a1e5628 (software/slapos-sr-testing: use nxdtest, 2020-10-28)
1 job for wip/repair-py3-sr-test in 0 seconds
Status Job ID Name Coverage
  External
canceled SlapOS.SoftwareReleases.IntegrationTest-Jerome-Python3

03:57:40