Remove interfaces

compiler/NubLang/Tokenization/Token.cs

@@ -67,7 +67,6 @@ public enum Symbol
     Ampersand,
     Let,
     Calls,
-    Interface,
     For,
     Extern,
     Semi,

compiler/NubLang/Tokenization/Tokenizer.cs

@@ -17,7 +17,6 @@ public sealed class Tokenizer
         ["struct"] = Symbol.Struct,
         ["let"] = Symbol.Let,
         ["calls"] = Symbol.Calls,
-        ["interface"] = Symbol.Interface,
         ["for"] = Symbol.For,
         ["extern"] = Symbol.Extern,
         ["module"] = Symbol.Module,