0.15.31

• [BUGFIX] Include all requirement files in the sdist (#6292) (thanks @xhochy)
• [DOCS] Updates outdated batch_request snippet in Terms (#6283)
• [DOCS] Update Conditional Expectations doc w/ current availability (#6279)
• [DOCS] Remove outdated Data Discovery page and all references (#6288)
• [DOCS] Remove reference/evaluation_parameters page and all references (#6294)
• [DOCS] Removing deprecated Custom Metrics doc (#6282)
• [DOCS] Re-writes "how to implement custom notifications" as "How to get Data Docs URLs for use in custom Validation Actions" (#6281)
• [DOCS] Removes deprecated expectation notebook exploration doc (#6298)
• [MAINTENANCE] Move RuleState into rule directory. (#6284)