Existing documentation was amended to point to correct usage of ilab model train command. The help message of CLI argument --data-path was added to explain interaction with --pipeline argument. The error message was rewritten to explain the most likely cause of the problem.

Resolves #2257

Checklist:

• Commit Message Formatting: Commit titles and messages follow guidelines in the
  conventional commits.
• Changelog updated with breaking and/or notable changes for the next minor release.
• Documentation has been updated, if necessary.
• Unit tests have been added, if necessary.
• Functional tests have been added, if necessary.
• E2E Workflow tests have been added, if necessary.