replaced .gitlab-ci.yml with latest version (dropping python 2)

2 jobs for update-pytorch in 6 minutes and 7 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #154901
docker
build_linux_36

00:06:05

90.0%
passed #154902
macosx
build_macosx_36

00:03:05