DOC: Fix building_your_first_artkit_pipeline.ipynb

[Tiger-Du]

Description

This PR is to remove an unused variable, prompt, from building_your_first_artkit_pipeline.ipynb as described in Issue #70.

It turns out that prompt is a duplicate of another variable named question in the previous cell.

In addition, question is used in a function call in the same cell as prompt, and since the definition of question is not in the immediate context (it is in the previous cell), I thought that it would be nice to modify the comment above the function call so that its use might be more clear to readers.

Issue number and link: #70

PR checks:

• [x] Have you followed our PR guidelines document
• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• [ ] Have you set these PR fields: Reviewers, Assignees, Labels, Milestones
• [ ] Have you updated RELEASE_NOTES.rst, if applicable?
• [ ] Have you updated existing and/or created new unit tests for your changes?