fix formdata constructor args mark optional (#4411)

* fix formdata constructor args mark optional

* fixup

* Update test/fetch/formdata.js

Co-authored-by: Khafra <maitken033380023@gmail.com>

---------

Co-authored-by: Khafra <maitken033380023@gmail.com>

Author: tsctx

lib/web/fetch/formdata.js

@@ -9,7 +9,7 @@ const nodeUtil = require('node:util')
 class FormData {
   #state = []
 
-  constructor (form) {
+  constructor (form = undefined) {
     webidl.util.markAsUncloneable(this)
 
     if (form !== undefined) {

test/fetch/formdata.js

@@ -341,7 +341,7 @@ test('FormData should be compatible with third-party libraries', (t) => {
 })
 
 test('arguments', () => {
-  assert.strictEqual(FormData.constructor.length, 1)
+  assert.strictEqual(FormData.length, 0)
   assert.strictEqual(FormData.prototype.append.length, 2)
   assert.strictEqual(FormData.prototype.delete.length, 1)
   assert.strictEqual(FormData.prototype.get.length, 1)