Update langchain_multimodal_rag.ipynb to support recept API updates

[drobison00]

Small update set that brings the langchain_multimodal_rag example into line with recent API updates.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

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[ChrisJar]

#141 consolidates the embedding and upload to milvus into the NV-Ingest job rather than doing it with Langchain, so that'll need to be updated when #141 goes in, but other than that LGTM!