Fix syntax

Author: sawoz

jscomp/others/node_buffer.ml

@@ -38,7 +38,7 @@ external fromStringWithEncoding : string -> ([ `ascii  | `utf8  | `utf16le  | `u
 external toString : t -> string = "toString"
 [@@bs.send]
 
-external toStringWithEncoding : (t, [ `ascii  | `utf8  | `utf16le  | `usc2  | `base64  | `latin1 | `binary  | `hex ] [@bs.string]) -> string = "toString"
+external toStringWithEncoding : t -> ([ `ascii  | `utf8  | `utf16le  | `usc2  | `base64  | `latin1 | `binary  | `hex ] [@bs.string]) -> string = "toString"
 [@@bs.send]
 
 external concat : t array -> t = "Buffer.concat"