Fix xunit dependency range.

Author: kurtschelfthout

Directory.Packages.props

@@ -33,10 +33,10 @@
     <PackageVersion Include="System.Threading" Version="4.3" />
     <PackageVersion Include="System.Threading.Tasks" Version="4.3" />
     <PackageVersion Include="Unquote" Version="6.0" />
-    <PackageVersion Include="xunit" Version="2.4.1" />
-    <PackageVersion Include="xunit.core" Version="2.4.1" />
-    <PackageVersion Include="xunit.extensibility.core" Version="2.4.1" />
-    <PackageVersion Include="xunit.extensibility.execution" Version="2.4.1" />
+    <PackageVersion Include="xunit" Version="[2.4.1, 3.0.0)" />
+    <PackageVersion Include="xunit.core" Version="[2.4.1, 3.0.0)" />
+    <PackageVersion Include="xunit.extensibility.core" Version="[2.4.1, 3.0.0)" />
+    <PackageVersion Include="xunit.extensibility.execution" Version="[2.4.1, 3.0.0)" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="2.5.7" />
   </ItemGroup>
 </Project>