Bump the dotnet group across 1 directory with 3 updates

Bumps the dotnet group with 3 updates in the /docs/fundamentals/networking/telemetry/snippets/metrics directory: [Microsoft.Extensions.Diagnostics.Testing](https://github.com/dotnet/extensions), [Microsoft.Extensions.Http](https://github.com/dotnet/runtime) and [xunit](https://github.com/xunit/xunit).


Updates `Microsoft.Extensions.Diagnostics.Testing` from 8.9.1 to 9.0.0
- [Release notes](https://github.com/dotnet/extensions/releases)
- [Commits](dotnet/extensions@v8.9.1...v9.0.0)

Updates `Microsoft.Extensions.Http` from 8.0.0 to 9.0.0
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v8.0.0...v9.0.0)

Updates `xunit` from 2.9.0 to 2.9.2
- [Commits](xunit/xunit@v2-2.9.0...v2-2.9.2)

---
updated-dependencies:
- dependency-name: Microsoft.Extensions.Diagnostics.Testing
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: dotnet
- dependency-name: Microsoft.Extensions.Http
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: dotnet
- dependency-name: xunit
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: dotnet
...

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

docs/fundamentals/networking/telemetry/snippets/metrics/HelloBuiltinMetrics.csproj

@@ -9,9 +9,9 @@
 
   <ItemGroup>
     <PackageReference Include="OpenTelemetry.Exporter.Prometheus.HttpListener" Version="1.7.0-rc.1" />
-    <PackageReference Include = "Microsoft.Extensions.Http" Version = "8.0.0" />
-    <PackageReference Include="xunit" Version="2.9.0" />
-    <PackageReference Include="Microsoft.Extensions.Diagnostics.Testing" Version="8.9.1" />
+    <PackageReference Include = "Microsoft.Extensions.Http" Version = "9.0.0" />
+    <PackageReference Include="xunit" Version="2.9.2" />
+    <PackageReference Include="Microsoft.Extensions.Diagnostics.Testing" Version="9.0.0" />
   </ItemGroup>
 
 </Project>