Update xUnit to 2.6.0.

Author: bgrainger

src/AdoNet.Specification.Tests/AdoNet.Specification.Tests.csproj

@@ -33,8 +33,8 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="xunit" Version="2.5.3" />
-    <PackageReference Include="xunit.extensibility.execution" Version="2.5.3" />
+    <PackageReference Include="xunit" Version="2.6.0" />
+    <PackageReference Include="xunit.extensibility.execution" Version="2.6.0" />
     <PackageReference Include="Xunit.SkippableFact" Version="1.4.13" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="All" />
   </ItemGroup>

tests/Directory.Build.props

@@ -1,7 +1,7 @@
 <Project>
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.7.2" />
-    <PackageReference Include="xunit" Version="2.5.3" />
+    <PackageReference Include="xunit" Version="2.6.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.5.3" />
   </ItemGroup>
 </Project>