Update Sonic Rush Theme and Delete Corkboard (#235)

* Update Sonic Rush Theme 

Its been two years...

* Delete The Corkboard

I don't like this theme anymore

* Update README.md

Change it to reflect Corkboard's removal

README.md

@@ -15,7 +15,7 @@ Scan this QR code in Universal-Updater to add a UniStore with these skins for ea
 ## Theme Credits:
 - [Allinxter](https://github.com/Allinxter): 3DS Kyurem, Tower Duo, The Legend of Zelda, Windows XP, Windows 7, Spider-Man, The Binding of Isaac, Phantom Thieves, Investigation Team, S.E.E.S., iDS, Terraria, Ace Attorney and Chrono Trigger skins, and DSi Persona 5 skin
 - [blloop](https://github.com/blloop): Grand Theft Auto CW Skin
-- [ctutts14](https://github.com/ctutts14): 3DS Sonic Rush and Corkboard Skins and Unlaunch Sonic Rush background
+- [ctutts14](https://github.com/ctutts14): 3DS Sonic Rush Skin and Unlaunch Sonic Rush background
 - [Dhalian.](https://github.com/Dhalian): 3DS Douze Coups de Midi skin, Unlaunch Douze Coups de Midi background 
 - doomguy9: DSi Breaking Bad skin
 - [DVDo](https://github.com/DieGo367): DSi Minecraft, Relaxing Space, Bowser's Fury, and Lake Lapcat skins