Get rid of extra using

Author: aonkeeper4

src/DashStates/DreamTunnelDash/DreamTunnelDash.cs

@@ -4,7 +4,6 @@
 using MonoMod.Cil;
 using MonoMod.RuntimeDetour;
 using MonoMod.Utils;
-using On.Celeste.Mod;
 using System.Linq;
 using System.Reflection;