For some reason, we used both `OPENAI_KEY` and `OPENAI_API_KEY` env variables, expecting them to have the same values. Drop the `OPENAI_KEY` one, since we document our use of `OPENAI_API_KEY`.

This test point runs fine on multiple dev machines (with updated Ollama), but fails in CI with an internal error to Ollama/llama.cpp:

```
  ================================================================================
  Error occurred in tollamaChat/generateWithImages and it did not run to completion.
      ---------
      Error ID:
      ---------
      'llms:apiReturnedError'
      --------------
      Error Details:
      --------------
      Error using ollamaChat/generate (line 238)
      Server returned error indicating: "an unknown error was encountered while
      running the model GGML_ASSERT(i01 >= 0 && i01 < ne01) failed"

      Error in tollamaChat>@(~)generate(chat,messages) (line 136)
                  text = arrayfun(@(~) generate(chat,messages), 1:5,
                  UniformOutput=false);

      Error in tollamaChat/generateWithImages (line 136)
                  text = arrayfun(@(~) generate(chat,messages), 1:5,
                  UniformOutput=false);
  ================================================================================
```

See also ollama/ollama#7288

Remove configuration for codecov

Using `dlarray` in a prototype results in `dlarray` in the output, but without the dimension labels. Reason: `cast(X,'like',Y)` behaves that way for `dlarray` `Y`.

Given that we do not return higher-dimensional data anyway, it is questionable whether there is any reason one would want to allow `dlarray` in prototypes. Not handling them properly means we are better off disabling them altogether.

Without a dependency on Deep Learning Toolbox, we cannot have an automated test point for this change, unfortunately.

Add Enrico as code owner

`azureChat` should support `ToolChoice="none"`

Make `azureChat` handle tool calls returned the same way we do in `openAIChat`.

Since we now throw an error when `ResponseFormat="json"` is used without
the required `"json"` in the inputs, we can stop warning in the constructor.
With the previous state, users got a warning they could not avoid, even
in code doing everything correctly.

change example to using structured output

* Activate structured output for ollamaChat
* Update documentation