Align intent_mapping.prompty deployment with .env (gpt-4o-mini)

[TemidireAdesiji]

Description

The azure_deployment field in scenarios/rag/custom-rag-app/assets/intent_mapping.prompty was set to gpt-4o, but the sample's runtime configuration uses gpt-4o-mini: .env.sample sets INTENT_MAPPING_MODEL="gpt-4o-mini", and get_product_documents.py reads the model from that variable. This one-line change aligns the prompt template with the documented .env configuration so the two no longer disagree, removing a point of confusion for anyone reviewing or modifying the sample.

Closes #262.

Checklist

• I have read the contribution guidelines
• I have coordinated with the docs team (mldocs@microsoft.com) if this PR deletes files or changes any file names or file extensions. (N/A: no files are deleted, renamed, or changed extension.)
• This notebook or file is added to the CODEOWNERS file, pointing to the author or the author's team. (N/A: this edits an existing file; no new file is added.)

[s-polly]

Approved for docs