Update Weaviate examples for client 4.16 API

[henry3260]

What

Update Weaviate system example Dags for the Python client 4.16 vector configuration API.

The examples now use vector_config / Configure.Vectors instead of the deprecated
vectorizer_config / Configure.Vectorizer, and explicitly use
Configure.Vectors.self_provided() where vectors are supplied by the Dag.

The provider now requires weaviate-client>=4.16.4,!=4.16.7 to use the new API
while avoiding the documented 4.16.0-4.16.3 invalid-properties behavior and the
known 4.16.7 protobuf issue.

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• Yes (please specify the tool below)

---

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[henry3260]

cc @Lee-W