[AIR] Fix //doc/source/ray-air/examples:feast_example

[jiaodong]

What happened + What you expected to happen

Notebook is broken due to bad import first, maybe more issues down the road. we're creating this issue to keep track of it.

Versions / Dependencies

master

Reproduction script

bazel test //doc/source/ray-air/examples:feast_example

Issue Severity

Medium: It is a significant difficulty but I can work around it.