Bump System.Diagnostics.DiagnosticSource (#43444)

Bumps the dotnet group in /docs/core/diagnostics/snippets/Metrics with 1 update: [System.Diagnostics.DiagnosticSource](https://github.com/dotnet/runtime).


Updates `System.Diagnostics.DiagnosticSource` from 8.0.1 to 9.0.0
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v8.0.1...v9.0.0)

---
updated-dependencies:
- dependency-name: System.Diagnostics.DiagnosticSource
  dependency-type: direct:production
  update-type: version-update:semver-major
  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/core/diagnostics/snippets/Metrics/metric-instr.csproj

@@ -9,7 +9,7 @@
 
   <ItemGroup>
     <PackageReference Include="OpenTelemetry.Exporter.Prometheus.HttpListener" Version="1.6.0-rc.1" />
-    <PackageReference Include="System.Diagnostics.DiagnosticSource" Version="8.0.1" />
+    <PackageReference Include="System.Diagnostics.DiagnosticSource" Version="9.0.0" />
   </ItemGroup>
 
 </Project>