Fix side effecting ember cli htmlbars import

[NullVoxPopuli]

rollup & co will try to optimize our v2 addons for runtime by hoisting the ember-cli-htmlbars to the toppest entry module.

during an app's build time, we need to remove that.

[ef4]

We discussed this during embroider office hours and concluded that hoistTransitiveImports is a better solution. This plugin doesn't support side-effectful import of ember-cli-htmlbars because it doesn't mean anything, so we can stop rollup from adding that. In general we don't want rollup to try to do this kind of whole-app optimization when we are merely building a v2 addon for publication.