Bump the dotnet group with 1 update (#49581)

Bumps OpenAI from 2.5.0 to 2.6.0

---
updated-dependencies:
- dependency-name: OpenAI
  dependency-version: 2.6.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: dotnet
...

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

Author: dependabot[bot]

docs/ai/quickstarts/snippets/assistants/AIAssistants.csproj

@@ -10,7 +10,7 @@
   <ItemGroup>
     <PackageReference Include="Azure.AI.OpenAI" Version="2.1.0" />
     <PackageReference Include="Azure.Identity" Version="1.17.0" />
-    <PackageReference Include="OpenAI" Version="2.5.0" />
+    <PackageReference Include="OpenAI" Version="2.6.0" />
   </ItemGroup>
 
 </Project>