[BUGFIX release] importing ember-source/types no longer works (it should)

[NullVoxPopuli]

Resolves: #20789

Which allows folks to use:

import 'ember-source/types';

in some ts file.

or

types: ['ember-source/types']

in tsconfig.json

Tested locally:

And one additional error state (which is reality before this PR)

[kategengler]

You tagged this release -- does it affect 6.0 or only 6.1?

[NullVoxPopuli]

It does affect 6.0, yes