Fix minor issues with LLM example documentation

[dagardner-nv]

Description

• Agents: Show an actual runnable command that can be copy/pasted, not just the command usage.
• Completion: Remove blank line in command block
• RAG: Remove section about fetching data, RAG doesn't need any LFS files.
• VDB Upload: Pipeline requires the examples dataset not the datasets dataset.
• VDB Upload: Document how to run Milvus

Closes #1991

By Submitting this PR I confirm:

• I am familiar with the Contributing Guidelines.
• When the PR is ready for review, new or existing tests cover these changes.
• When the PR is ready for review, the documentation is up to date with these changes.

[dagardner-nv]

/merge