Bump the tests group with 1 update

Bumps Microsoft.NET.Test.Sdk from 18.7.0 to 18.8.1

---
updated-dependencies:
- dependency-name: Microsoft.NET.Test.Sdk
  dependency-version: 18.8.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: tests
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

src/Tests/Tests.csproj

@@ -5,7 +5,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="coverlet.collector" Version="10.0.1" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.7.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.8.1" />
     <PackageReference Include="xunit" Version="2.9.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5" />
   </ItemGroup>