Remove implicit this for now

example/src/main.nub

@@ -1,16 +1,6 @@
 extern func puts(fmt: cstring)
 
-interface Printable
-{
-    func print()
-}
-
-interface Stringable
-{
-    func str(): cstring
-}
-
-struct Human : Printable, Stringable
+struct Human
 {
     name: cstring
 
@@ -18,11 +8,6 @@ struct Human : Printable, Stringable
     {
         return this.name
     }
-
-    func print()
-    {
-        puts(this.str())
-    }
 }
 
 func main(args: []cstring): i64
@@ -32,7 +17,6 @@ func main(args: []cstring): i64
     }
 
     puts(human.str())
-    // human.print()
 
     return 0
 }