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

Ref: PACT-445

Author: pactflow-renovate-bot[bot]

tests/tests.csproj

@@ -11,7 +11,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.0" />
     <PackageReference Include="PactNet" Version="5.0.1" />
     <PackageReference Include="PactNet.Output.Xunit" Version="1.0.0" />
     <PackageReference Include="xunit" Version="2.9.3" />