use false instead of null to hide the currency symbol

This slipped in with #61296. Technically, there shouldn't be a difference
but since we explicitly mention false in the documentation let's better
be safe here.

Author: xabbuh

Tests/Extension/Core/Type/MoneyTypeTest.php

@@ -76,7 +76,7 @@ public function testSubmitNull($expected = null, $norm = null, $view = null)
 
     public function testMoneyPatternWithoutCurrency()
     {
-        $view = $this->factory->create(static::TESTED_TYPE, null, ['currency' => null])
+        $view = $this->factory->create(static::TESTED_TYPE, null, ['currency' => false])
             ->createView();
 
         $this->assertSame('{{ widget }}', $view->vars['money_pattern']);