Examples Should Avoid Using Schema Registry for Keys

I don't think it's commonly understood by new learners that using Schema Registry for keys is bad practice (see this internal confluent [slack convo](https://confluent.slack.com/archives/GALQHUBEG/p1598908733004000) ). For example, if you reorder fields, it will break partitioning. Also protobuf and json schemas don't serialize deterministically, so using those formats for keys will also break partitioning.

[This python example](https://github.com/confluentinc/examples/tree/6.0.0-post/clients/cloud/python) uses Avro for the key `Name` and it probably shouldn't.