[NO GBP] Makes Iron Sheets less shiny (tgstation#72778)

## About The Pull Request
What it says on the tin

![image](https://user-images.githubusercontent.com/66052067/213025761-5166bfd6-2559-4032-9860-0107e93883d7.png)

![image](https://user-images.githubusercontent.com/66052067/213025988-55034b81-075a-4d53-b44a-d3cf39d4991a.png)

## Why It's Good For The Game
A lot of the response to the material resprites has been that it's too
difficult to tell some of the sheets apart, so to help fix that we've
made it so the iron is no longer shiny, which both fits more with its
previous iteration as well as makes it easier to tell apart from glass
and titanium.
## Changelog
:cl: Wallem
imageadd: Made the station's iron sheets less shiny to increase sprite
legibility.
/:cl: