Format date unit tests is now working

tests/PhpSpreadsheet/Style/NumberFormatDateTest.php

@@ -18,8 +18,6 @@ class NumberFormatDateTest extends \PHPUnit_Framework_TestCase
      */
     public function testFormatValueWithMask()
     {
-        $this->markTestIncomplete('TODO: This test should be fixed');
-
         $args = func_get_args();
         $expectedResult = array_pop($args);
         $result = call_user_func_array([NumberFormat::class, 'toFormattedString'], $args);