Revert "Merge branch '58927-jupyterhub-fails-to-install' into 'master'"

What does this MR do?

Jupyter installation will be fixed when RC6 lands in production with this particular change https://gitlab.com/gitlab-org/gitlab-ce/blob/v11.9.0-rc6/app/models/clusters/applications/jupyter.rb. So disabling the prePuller option is not required.

Does this MR meet the acceptance criteria?

• [-] Changelog entry added, if necessary
• [-] Documentation created/updated via this MR
• [-] Documentation reviewed by technical writer or follow-up review issue created
• [-] Tests added for this feature/bug
• [-] Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• [-] Conforms to the database guides
• [-] Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• [-] Security reports checked/validated by reviewer