chore: update documentation MR template

Description

The merge request template for documentation updates has been slightly modified: a new label ~"section::ai" has been added to the list of labels that get automatically applied when the template is used. This helps ensure documentation MRs are properly categorized under the AI section for better tracking and organization.

Documentation

If this MR adds or updates CLI command documentation, follow the conventions in the GitLab CLI (glab) documentation style guide, run make gen-docs, and commit the updated files in docs/source/.