fix: fix 'reporters' key name in karma.conf (#433)

Followup to angular/material.angular.io#431

Author: richdev350

karma.conf.js

@@ -23,7 +23,7 @@ module.exports = function (config) {
       reports: ['html', 'lcovonly'],
       fixWebpackSourcePaths: true
     },
-    rreporters: ['progress', 'kjhtml'],
+    reporters: ['progress', 'kjhtml'],
     port: 9876,
     colors: true,
     logLevel: config.LOG_INFO,