build(deps): bump xunit.core from 2.5.3 to 2.6.0 (#39)

Author: dependabot[bot]

Directory.Packages.props

@@ -16,7 +16,7 @@
     <PackageVersion Include="Polyfill" Version="1.29.0" />
     <PackageVersion Include="Verify.Xunit" Version="22.1.4" />
     <PackageVersion Include="xunit" Version="2.5.1" />
-    <PackageVersion Include="xunit.core" Version="2.5.3" />
+    <PackageVersion Include="xunit.core" Version="2.6.0" />
     <PackageVersion Include="xunit.runner.console" Version="2.5.3" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="2.4.5" />
   </ItemGroup>