chore(deps): update dependency microsoft.net.test.sdk to v18

Author: renovate[bot]

src/Directory.build.props

@@ -31,7 +31,7 @@
 
 	<ItemGroup Condition="'$(IsTestProject)' == 'true'">
 		<PackageReference Include="ReactiveUI.Testing" Version="21.*" />
-		<PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+		<PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.0" />
 		<PackageReference Include="xunit" Version="2.9.3" />
 		<PackageReference Include="xunit.runner.console" Version="2.9.3" />
 		<PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />