Update dependency xunit.v3 to v2

Author: renovate[bot]

Lombiq.HelpfulLibraries.Tests/Lombiq.HelpfulLibraries.Tests.csproj

@@ -18,7 +18,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.13.0" />
-    <PackageReference Include="xunit.v3" Version="1.1.0" />
+    <PackageReference Include="xunit.v3" Version="2.0.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.0.2">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>