fixing invalid import

[ef4]

There is no defaultRules export from ./lib/system, so this was a SyntaxError in any system that faithfully follows the module spec.

[ef4]

I think the test failure here is because ember-try is using NPM 7, which hard errors on a missing peer dependency. But I don't see why it should be missing. @embroider/hbs-loader has a peerDep on webpack, and those two packages are in fact peers under @embroider/webpack. Maybe something about ember-try is interacting oddly with npm 7.