Fix spelling error in webpackWorker comment

src/webpackWorker.js

@@ -77,7 +77,7 @@ module.exports = function(configuratorFileName, options, index, expectedConfigLe
             || Array.isArray(config) && config.length !== expectedConfigLength) {
         if(config.length !== expectedConfigLength) {
             var errorMessage = '[WEBPACK] There is a difference between the amount of the'
-                + ' provided configs. Maybe you where expecting command line'
+                + ' provided configs. Maybe you were expecting command line'
                 + ' arguments to be passed to your webpack.config.js. If so,'
                 + " you'll need to separate them with a -- from the parallel-webpack options.";
             console.error(errorMessage);