Remove kbatch, prefect and clearml

[iameskild]

Reference Issues or PRs

Closes #1217

What does this implement/fix?

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds a feature)
• Breaking change (fix or feature that would cause existing features not to work as expected)
• Documentation Update
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build related changes
• Other (please describe):

Testing

• Did you test the pull request locally?
• Did you add new tests?

Any other comments?

[dcmcand]

upgrade.py still says that they are depreciated and will be removed in the next release. Should that be editted now since it is out of date?

[iameskild]

@dcmcand when they run the nebari upgrade command, the user will be, among other things, presented with messages that we may want them to be aware of. I believe we should keep those messages since they might still be helpful to read for folks upgrading from an older version of Nebari to this latest version.