Transform 'let' in 'const' where needs be

helloWorld/helloWorld.spec.js

@@ -1,7 +1,7 @@
-let helloWorld = require('./helloWorld');
+const helloWorld = require('./helloWorld');
 
 describe('Hello World', function() {
   it('says hello world', function() {
     expect(helloWorld()).toEqual('Hello, World!');
   });
-});
+});