Remove jni-docker-build workflow (#15619)

This PR removes `jni-docker-build.yml`, which is an unused workflow according to the Spark team.

Authors:
  - Bradley Dice (https://github.com/bdice)

Approvers:
  - Ray Douglass (https://github.com/raydouglass)
  - Tim Liu (https://github.com/NvTimLiu)

URL: #15619