Bump Microsoft.AspNetCore.OpenApi from 8.0.12 to 8.0.13 in /src

Bumps [Microsoft.AspNetCore.OpenApi](https://github.com/dotnet/aspnetcore) from 8.0.12 to 8.0.13.
- [Release notes](https://github.com/dotnet/aspnetcore/releases)
- [Changelog](https://github.com/dotnet/aspnetcore/blob/main/docs/ReleasePlanning.md)
- [Commits](dotnet/aspnetcore@v8.0.12...v8.0.13)

---
updated-dependencies:
- dependency-name: Microsoft.AspNetCore.OpenApi
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

src/GraphEventGrid.csproj

@@ -15,7 +15,7 @@
 
   <ItemGroup>
     <PackageReference Include="Azure.Identity" Version="1.13.2" />
-    <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="8.0.12" />
+    <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="8.0.13" />
     <PackageReference Include="Microsoft.Graph" Version="5.70.0" />
     <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.556">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>