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 3d34986.

Author: pmowrer

CHANGELOG.md

@@ -1,11 +1,10 @@
 # Changelog
 
-Deprecated. For versions above **4.1.0**, please refer to "Releases" in GitHub UI.
+## *Deprecated* 
+For versions above **4.1.0**, please refer to "Releases" in GitHub UI.
 
 ## 4.1.0
 
-- Return `fileName` to have sass-loader handle dependency correctly (#74).
-
 ## 4.0.1
 * Update package.json's main field (#73).