Clarify missing css file error message.

 * Fixed redundant quotes due to colour.

Author: RolfBabijn

lib/friendly-errors/formatters/missing-loader.js

@@ -24,7 +24,7 @@ function formatErrors(errors) {
 
         if (error.loaderName) {
             let neededCode = `Encore.${loaderFeatures.getFeatureMethod(error.loaderName)}`;
-            fixes.push(`Add '${chalk.green(neededCode)}' to your webpack.config.js file.`);
+            fixes.push(`Add ${chalk.green(neededCode)} to your webpack.config.js file.`);
 
             const packageRecommendations = loaderFeatures.getMissingPackageRecommendations(error.loaderName);