Transitive dependencies have wrong restriction

This seems to be similar to #1213.

I have a web app that I've split into two projects so the EF stuff can be in C# and the rest in F#.

So the initial paket.dependencies looks like this:

source https://api.nuget.org/v3/index.json

nuget Microsoft.AspNetCore.App
nuget Microsoft.EntityFrameworkCore.SqlServer

The paket.lock file ends up with this for the EF package:

Microsoft.EntityFrameworkCore.SqlServer (2.1)
  Microsoft.EntityFrameworkCore.Relational (>= 2.1) - restriction: >= netstandard2.0
  System.Data.SqlClient (>= 4.5) - restriction: >= netstandard2.0

As the EF bits are also pulled in by the meta-package, I would have thought (and paket simplify agrees) that Microsoft.EntityFrameworkCore.SqlServer can be removed from paket.dependencies. If I do this, remove paket.lock and run paket install again, then a bunch of restrictions change. The previous excerpt becomes this:

Microsoft.EntityFrameworkCore.SqlServer (2.1) - restriction: >= netcoreapp2.1
  Microsoft.EntityFrameworkCore.Relational (>= 2.1) - restriction: >= netstandard2.0
  System.Data.SqlClient (>= 4.5) - restriction: >= netstandard2.0

And now the EF project won't build because there's no package available for netstandard2.0.

I've created a minimal repro solution where you can see the diff between the paket.lock files.

Start with the minimal repro solution and compare the linked paket.lock diff. Read the paket.dependencies entries, then run paket simplify and paket install with and without the direct EF package. Done means the generated restrictions preserve the netstandard2.0 dependency and both projects build.