chore(deps): update dependency microsoft.net.test.sdk to 17.13.0

| datasource | package                | from    | to      |
| ---------- | ---------------------- | ------- | ------- |
| nuget      | Microsoft.NET.Test.Sdk | 17.12.0 | 17.13.0 |

Author: renovate[bot]

UnitTests/UnitTests.csproj

@@ -9,7 +9,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.13.0" />
         <PackageReference Include="xunit" Version="2.9.3" />
         <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2" />
         <ProjectReference Include="..\CSSParser\CSSParser.csproj" />