Bump the testing-frameworks group with 1 update (#1746)

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

Author: dependabot[bot]

Directory.Packages.props

@@ -75,7 +75,7 @@
     <PackageVersion Include="Microsoft.Extensions.Logging.Console" Version="$(System10Version)" />
     <PackageVersion Include="Microsoft.Extensions.Options" Version="$(System10Version)" />
     <PackageVersion Include="Microsoft.Extensions.TimeProvider.Testing" Version="10.1.0" />
-    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.5.1" />
+    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.8.1" />
     <PackageVersion Include="Moq" Version="4.20.72" />
     <PackageVersion Include="OpenTelemetry" Version="1.15.3" />
     <PackageVersion Include="OpenTelemetry.Exporter.InMemory" Version="1.15.3" />