Bump OpenAI (#43903)

Bumps the dotnet group in /docs/ai/quickstarts/snippets/image-generation/openai with 1 update: [OpenAI](https://github.com/openai/openai-dotnet).


Updates `OpenAI` from 2.1.0-beta.1 to 2.1.0
- [Release notes](https://github.com/openai/openai-dotnet/releases)
- [Changelog](https://github.com/openai/openai-dotnet/blob/main/CHANGELOG.md)
- [Commits](openai/openai-dotnet@OpenAI_2.1.0-beta.1...OpenAI_2.1.0)

---
updated-dependencies:
- dependency-name: OpenAI
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: dotnet
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

docs/ai/quickstarts/snippets/image-generation/openai/ImagesOpenAI.csproj

@@ -8,7 +8,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="OpenAI" Version="2.1.0-beta.1" />
+    <PackageReference Include="OpenAI" Version="2.1.0" />
     <PackageReference Include="Microsoft.Extensions.AI.OpenAI" Version="9.0.0-preview.9.24556.5" />
     <PackageReference Include="Microsoft.Extensions.Configuration" Version="9.0.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.UserSecrets" Version="9.0.0" />