Move Jupyter notebooks from repository to packages

What does this MR do?

This MR moves the documentation for Jupyter from the repository section to Packages. This correlates with the recent change to add Jupyter to the Package Stage.

I did not move the two sections under managed apps, because it felt like I would have been duplicating content.

This was originally discussed via slack: https://gitlab.slack.com/archives/C3MAZRM8W/p1579106633073300?thread_ts=1578983196.058800&cid=C3MAZRM8W

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team