chore(testing): correct typo in karma.conf builtPaths (#2963)

Author: wardbell

public/docs/_examples/testing/ts/karma.conf.js

@@ -20,7 +20,7 @@ module.exports = function(config) {
     ],
 
     client: {
-      builtPaths: [appSrcBase, testingBase], // add more spec base paths as needed
+      builtPaths: [appBase, testingBase], // add more spec base paths as needed
       clearContext: false // leave Jasmine Spec Runner output visible in browser
     },