[ZEPPELIN-6508] Remove outdated Mahout interpreter helper and documentation

[jongyoul]

What is this PR for?

Remove the obsolete Mahout integration artifacts from Zeppelin.

The existing mahout.md page does not describe a standalone Zeppelin interpreter module. It relies on a Python 2 helper that clones the Spark and Flink interpreter settings, then adds Mahout 0.12.2 artifacts built for Scala 2.10. The accompanying documentation and tutorial are limited to Spark 1.5/1.6 and no longer match Zeppelin's supported runtime stack.

This PR removes the helper, its documentation and navigation entries, and the bundled Mahout tutorial notebook. Apache Mahout's current Qumat Python packages use a separate Python integration path and are intentionally outside the scope of this cleanup PR.

What type of PR is it?

Improvement

Todos

• Remove the legacy Mahout helper script
• Remove the obsolete Mahout interpreter documentation and navigation entries
• Remove the bundled Mahout tutorial notebook
• Verify that no Mahout or Qumat references remain in the repository

What is the Jira issue?

https://issues.apache.org/jira/browse/ZEPPELIN-6508

How should this be tested?

• bundle exec jekyll build --safe in the documented Ruby 4.0.6 Docker environment
• ruby check_external_resources.rb _site
• git diff --check
• Verify that the generated site contains no Mahout page or navigation entry
• Verify that the repository contains no remaining Mahout or Qumat references

Screenshots (if appropriate)

Not applicable.

Questions:

• Does the license files need to update? No.
• Is there breaking changes for older versions? The PR removes unsupported legacy documentation, a helper script, and a tutorial notebook; no interpreter module or supported runtime behavior is changed.
• Does this needs documentation? This PR removes the obsolete documentation and all links to it.

[Copilot]

Pull request overview

Warning

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Removes obsolete Apache Mahout integration artifacts from Zeppelin’s repository and website to align documentation and helpers with the currently supported runtime stack.

Changes:

• Removed the legacy Mahout interpreter helper script.
• Removed the Mahout interpreter documentation page.
• Removed Mahout links from the docs index and site navigation.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

File	Description
scripts/mahout/add_mahout_interpreters.py	Deletes the legacy Python 2 helper that cloned interpreter settings and injected Mahout dependencies.
docs/interpreter/mahout.md	Removes outdated Mahout interpreter documentation tied to old Spark/Flink/Scala versions.
docs/index.md	Removes the Mahout interpreter entry from the documentation index.
docs/_includes/themes/zeppelin/_navigation.html	Removes the Mahout interpreter link from the site navigation menu.

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