revert: "Return fileName to have sass-loader handle dependency correctly"
revert: "Return fileName to have sass-loader handle dependency correctly"

Reverts feature adding `fileName` field to the returned object, because
[returning both `fileName` and `contents` is unexpected per the docs](https://sass-lang.com/documentation/js-api#importer)
breaking the importer, as reported in #78.

This reverts commit 3d349863b1fbefef7479914fe1558f2711dd713a.

Updater/node-sass-json-importer