Eliminate reference to `nunit.engine` by nunit-console runner

[CharliePoole]

This unintended reference crept in as part of an experiment, which didn't work out. The intention is for the runner to reference the engine only through nunit.engine.api.

[CharliePoole]

This issue has been resolved in version 4.0.0-beta.1

The release is available on:
GitHub.
NuGet packages are also available NuGet.org and
Chocolatey Packages may be found at Chocolatey.org