Downgrade to release image #39 to avoid issue with Sphinx [nocheck]
Downgrade to release image #39 to avoid issue with Sphinx [nocheck]

Image #40 breaks documentation - see internal discussion

https://h2oai.slack.com/archives/C04KNHH2H/p1631514069021100

h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3