Fix default processor signature

Fixes a bug that sneaked in fda810e and that was uncaught by the test suite.

Author: pmdartus

lib/context.js

@@ -10,7 +10,7 @@ const builtinTypedefs = webidl.parse(`
   typedef unsigned long long DOMTimeStamp;
 `);
 
-function defaultProcessor(_idl, code) {
+function defaultProcessor(code) {
   return code;
 }