Fix: (webpack.config.js) css-loader API change

The build was broken in
<https://github.com/pydata/pydata-sphinx-theme/commit/185a37aa36820f77bffa4c87a772092e9e7cc380>/<https://github.com/pydata/pydata-sphinx-theme/pull/1494>.

This change fixes the build, but may not be the best way to do so, as
I would guess it re-enables url()-inlining, which may be undesired.

Closes <#1507>.

Author: alphapapa

webpack.config.js

@@ -159,7 +159,7 @@ module.exports = {
       test: /\.scss$/,
       use: [
         {loader: MiniCssExtractPlugin.loader},
-        {loader: "css-loader?-url"}, //url()-inlining turned off
+        {loader: "css-loader"},
         {loader: "sass-loader",},
       ],
     }],