.Net: Update the integration tests readme to include instructions for…

… audio tests (#5051)

### Motivation and Context

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### Contribution Checklist

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---------

Co-authored-by: Dmytro Struk <13853051+dmytrostruk@users.noreply.github.com>

dotnet/src/IntegrationTests/README.md

@@ -45,6 +45,14 @@ dotnet user-secrets set "AzureOpenAIEmbeddings:DeploymentName" "text-embedding-a
 dotnet user-secrets set "AzureOpenAIEmbeddings:Endpoint" "https://contoso.openai.azure.com/"
 dotnet user-secrets set "AzureOpenAIEmbeddings:ApiKey" "..."
 
+dotnet user-secrets set "AzureOpenAIAudioToText:DeploymentName" "whisper-1"
+dotnet user-secrets set "AzureOpenAIAudioToText:Endpoint" "https://contoso.openai.azure.com/"
+dotnet user-secrets set "AzureOpenAIAudioToText:ApiKey" "..."
+
+dotnet user-secrets set "AzureOpenAITextToAudio:DeploymentName" "tts-1"
+dotnet user-secrets set "AzureOpenAITextToAudio:Endpoint" "https://contoso.openai.azure.com/"
+dotnet user-secrets set "AzureOpenAITextToAudio:ApiKey" "..."
+
 dotnet user-secrets set "HuggingFace:ApiKey" "..."
 dotnet user-secrets set "Bing:ApiKey" "..."
 dotnet user-secrets set "Postgres:ConnectionString" "..."