Ensure TestCommon project is not treated as a test project

Author: gunndabad

test/GovUk.FrontEnd.AspNetCore.TestCommon/GovUk.FrontEnd.AspNetCore.TestCommon.csproj

@@ -2,8 +2,13 @@
 
   <PropertyGroup>
     <TargetFrameworks>net6.0</TargetFrameworks>
+    <IsTestProject>false</IsTestProject>
   </PropertyGroup>
 
+  <ItemGroup>
+    <ProjectCapability Remove="TestContainer" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="AngleSharp.Diffing" Version="0.14.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.2.0" />