Bump Testcontainers from 3.10.0 to 4.0.0 (#19)

Author: dependabot[bot]

test/Styra.Opa.AspNetCore.Tests/Styra.Opa.AspNetCore.Tests.csproj

@@ -13,7 +13,7 @@
     <PackageReference Include="Microsoft.AspNetCore.TestHost" Version="8.0.10" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
-    <PackageReference Include="Testcontainers" Version="3.10.0" />
+    <PackageReference Include="Testcontainers" Version="4.0.0" />
     <PackageReference Include="xunit" Version="2.9.2" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>