Resprites Catwalk Tiles to match TG's floortiles (#84819)

## About The Pull Request
Forgive me Maintainers, for I have sinned.
Months ago, a year ago, maybe longer, I PR'd some new and improved
sprites for the Catwalk Tiles here to TG. And when I did, I did not use
the right tile palettes for reference.

I have come to atone.


![image](https://github.com/tgstation/tgstation/assets/76465278/16605b30-455c-4c17-863b-00451a76fe27)

![image](https://github.com/tgstation/tgstation/assets/76465278/2d91e1b0-37c9-4916-b02a-9b23db0e3028)

![image](https://github.com/tgstation/tgstation/assets/76465278/c4233dec-1871-42ac-848b-2e8e94454dbc)

![image](https://github.com/tgstation/tgstation/assets/76465278/d8f09852-a8aa-4093-a4fd-68ddcbbc51af)

![image](https://github.com/tgstation/tgstation/assets/76465278/ff219529-d91c-459c-b8dc-b95e44890fa6)

Additionally, I removed a duplicate white catwalk tile (flat_white - the
one left is iron_white) and changed the `none`/error icon in the file to
double as both an error marker, and a template of the catwalk mesh for
future catwalk tile sprites.
## Why It's Good For The Game
Consistent matching tile sprites are much, much nicer to look at.
## Changelog
🆑
image: re-sprited Catwalk Floor Tiles to fit with TG floor tiles
/🆑

tools/UpdatePaths/Scripts/84819_replace_flat_white_catwalks.txt

@@ -0,0 +1,5 @@
+# replaces redundant flat_white catwalk tiles with iron_white
+
+/turf/open/floor/catwalk_floor/flat_white : /turf/open/floor/catwalk_floor/iron_white{@OLD}
+/turf/open/floor/catwalk_floor/flat_white/@SUBTYPES : /turf/open/floor/catwalk_floor/iron_white/@SUBTYPES{@OLD}
+/obj/item/stack/tile/catwalk_tile/flat_white : /obj/item/stack/tile/catwalk_tile/iron_white{@OLD}