chore(webpack): disable style sourcemap on PROD

@@ -28,7 +28,7 @@ let assets = _.map(bundleConfig.vendor, (asset, name) => {
 let webpackConfig = merge(baseConfig, {
 let webpackConfig = merge(baseConfig, {
     module: {
     module: {
         rules: utils.styleLoaders({
         rules: utils.styleLoaders({
-            sourceMap: config.build.productionSourceMap,
+            sourceMap: false,
             extract: true
             extract: true
         })
         })
     },
     },