Modified sec backpack sprite

... so that it doesn't make the new armor sprites look dumb.

Before
![ab](https://f.cloud.github.com/assets/4343468/2444557/33859048-ae58-11e3-9baf-42874bbd6b19.png)

After
![aa](https://f.cloud.github.com/assets/4343468/2444558/365e2f96-ae58-11e3-8da1-5b748cff12ca.png)