Bump Microsoft.NET.Test.Sdk from 17.14.1 to 18.0.0 (#53)

Author: dependabot[bot]

test/OpenPolicyAgent.Ucast.Linq.Tests/OpenPolicyAgent.Ucast.Linq.Tests.csproj

@@ -10,7 +10,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <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.visualstudio" Version="3.1.4">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>