chore(test): drop EntityFrameworkCore.InMemory package

No tests use the InMemory provider anymore after migrating
UserPropertyAccess tests to Testcontainers + TestBaseSetup.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: renemadsen

eFormAPI/Plugins/BackendConfiguration.Pn/BackendConfiguration.Pn.Test/BackendConfiguration.Pn.Test.csproj

@@ -18,7 +18,6 @@
       <PackageReference Include="NUnit3TestAdapter" Version="6.2.0" />
       <PackageReference Include="Testcontainers" Version="4.11.0" />
       <PackageReference Include="Testcontainers.MariaDb" Version="4.11.0" />
-      <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" Version="10.0.5" />
     </ItemGroup>
 
     <ItemGroup>