.Net: Update to Azure.AI.OpenAI version 1.0.0-beta.6 (#2090)

### Motivation and Context
Utilize the latest version of the Azure.AI.OpenAI package. This provides
support for the latest Azure OpenAI REST API versions (including
function calling!) and fixes a minor regression.

Fixes #2089 

### Description

Update to Azure.AI.OpenAI version 1.0.0-beta.6 and fix minor regression.

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https:/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https:/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#dev-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

---------

Co-authored-by: Shawn Callegari <[email protected]>

dotnet/Directory.Packages.props

@@ -5,7 +5,7 @@
  <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
  </PropertyGroup>
  <ItemGroup>
- <PackageVersion Include="Azure.AI.OpenAI" Version="1.0.0-beta.5" />
+ <PackageVersion Include="Azure.AI.OpenAI" Version="1.0.0-beta.6" />
  <PackageVersion Include="Azure.Identity" Version="1.9.0" />
  <PackageVersion Include="Azure.Search.Documents" Version="11.5.0-beta.3" />
  <PackageVersion Include="Microsoft.ApplicationInsights.WorkerService" Version="2.21.0" />

dotnet/src/Connectors/Connectors.AI.OpenAI/AzureSdk/ClientBase.cs

@@ -318,7 +318,7 @@ private static ChatCompletionsOptions CreateChatCompletionsOptions(ChatRequestSe
  NucleusSamplingFactor = (float?)requestSettings.TopP,
  FrequencyPenalty = (float?)requestSettings.FrequencyPenalty,
  PresencePenalty = (float?)requestSettings.PresencePenalty,
- ChoicesPerPrompt = requestSettings.ResultsPerPrompt
+ ChoiceCount = requestSettings.ResultsPerPrompt
  };
 
  foreach (var keyValue in requestSettings.TokenSelectionBiases)

dotnet/src/SemanticKernel.Abstractions/AI/ChatCompletion/AuthorRole.cs

@@ -14,15 +14,15 @@ namespace Microsoft.SemanticKernel.AI.ChatCompletion;
  /// <summary>
  /// The role that instructs or sets the behavior of the assistant.
  /// </summary>
- public static readonly AuthorRole System = new("System");
+ public static readonly AuthorRole System = new("system");
  /// <summary>
  /// The role that provides responses to system-instructed, user-prompted input.
  /// </summary>
- public static readonly AuthorRole Assistant = new("Assistant");
+ public static readonly AuthorRole Assistant = new("assistant");
  /// <summary>
  /// The role that provides input for chat completions.
  /// </summary>
- public static readonly AuthorRole User = new("User");
+ public static readonly AuthorRole User = new("user");
 
  /// <summary>
  /// Gets the label associated with this AuthorRole.