ArgumentException when trying to generate client from Azure specification

### What are you generating using Kiota, clients or plugins?

API Client/SDK

### In what context or format are you using Kiota?

Nuget tool

### Client library/SDK language

Csharp

### Describe the bug

I am trying to create an API client based on https://raw.githubusercontent.com/Azure/azure-rest-api-specs/refs/heads/main/specification/ai/data-plane/OpenAI.v1/azure-v1-v1-generated.json and I observe an ArgumentException in FindChildByName and the client is not generated. Trying to use the specification with https://editor.swagger.io/ seems to work with some warnings. The problem seems to be with ResponseModalities, though not sure I understand why.

### Expected behavior

Generate client should work without an exception.

### How to reproduce

```
kiota generate --openapi https://raw.githubusercontent.com/Azure/azure-rest-api-specs/refs/heads/main/specification/ai/data-plane/OpenAI.v1/azure-v1-v1-generated.json --language CSharp --namespace-name Test --class-name Client --output Test --exclude-backward-compatible --serializer Microsoft.Kiota.Serialization.Json.JsonSerializationWriterFactory --deserializer Microsoft.Kiota.Serialization.Json.JsonParseNodeFactory --structured-mime-types application/json --include-path "**/chat/*" --clean-output
```

### Open API description file

https://raw.githubusercontent.com/Azure/azure-rest-api-specs/refs/heads/main/specification/ai/data-plane/OpenAI.v1/azure-v1-v1-generated.json

### Kiota Version

1.29.0

### Latest Kiota version known to work for scenario above?(Not required)

_No response_

### Known Workarounds

_No response_

### Configuration

_No response_

### Debug output

Click to expand log

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```

### Other information

_No response_

Start by running the reported Kiota 1.29.0 command against the linked Azure OpenAPI specification, then inspect the FindChildByName failure around ResponseModalities. Compare the behavior with the warnings from editor.swagger.io; done means the C# client is generated without an ArgumentException.

Written by the indexing model from the issue text.