fixed indentation of input.js comment

Request Type: docs

How to reproduce: 

Component(s): misc core

Impact: small

Complexity: small

This issue is related to: 

**Detailed Description:**

the doc's code block of `$formatter` in [http://docs.angularjs.org/api/ng/type/ngModel.NgModelController](http://docs.angularjs.org/api/ng/type/ngModel.NgModelController) looks like

![2014-03-12 21 17 53](https://f.cloud.github.com/assets/1506738/2397075/99dc7492-a9e4-11e3-9e42-77a54a2bd616.png)

So I fixed indentation of code block in `input.js` 


**Other Comments:**