Revert "Expose the original, uncompiled assets in importmaps"

[jcoyne]

This reverts commit b682c57.

The uncompiled assets make relative imports like:

import CheckboxSubmit from './checkbox_submit'

When this is used in a live site we would want it to be:

import CheckboxSubmit from 'blacklight/checkbox_submit'

So there would still be some needed precompilation step before importmap could use the individual modules.