Remove direct dependency on EFCore.Abstractions

Closes npgsql#3170

Author: roji

src/EFCore.PG/EFCore.PG.csproj

@@ -16,7 +16,6 @@
     <!-- PrivateAssets="none" is set to flow the EF Core analyzer to users referencing this package https://github.com/aspnet/EntityFrameworkCore/pull/11350 -->
     <PackageReference Include="Microsoft.EntityFrameworkCore" PrivateAssets="none" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Relational" PrivateAssets="none" />
-    <PackageReference Include="Microsoft.EntityFrameworkCore.Abstractions" PrivateAssets="none" />
     <PackageReference Include="Npgsql" />
   </ItemGroup>