How to not reference dependencies of Microsoft.NETCore.App for .NET Core console apps?

I have a brand-new .NET Core app. By default, .NET Core apps reference the Microsoft.NETCore.App NuGet package; I want to uninstall certain packages referenced by that, namely System.Collections.Immutable, so that I can't use the types in them from my app.

How do I do this when the Microsoft.NETCore.App reference is implicitly included? The packages installed by default aren't even mentioned in the .csproj file now, so how am I supposed to remove them?

Below is the contents of my .csproj file:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp1.1</TargetFramework>
  </PropertyGroup>

</Project>