Python: Missing load_dotenv in sample 05; incorrect env var docs in chat_response_cancellation

[amit12cool]

05_functional_workflow_with_agents.py uses FoundryChatClient without explicit constructor args but does not call load_dotenv(), causing silent failures for users with .env files. Also, chat_response_cancellation.py docstring incorrectly references OPENAI_MODEL/OPENAI_API_KEY instead of Foundry env vars.

[chetantoshniwal]

Thanks for the catch, we will get the PR merged.

[chetantoshniwal]

queued to merge.