Fix unit tests for WEEKDAY()

In Excel the expected value was incorrect (but it would be different
for LibreOffice)

tests/PhpSpreadsheetTests/Calculation/DateTimeTest.php

@@ -156,12 +156,9 @@ class DateTimeTest extends \PHPUnit_Framework_TestCase
 
     /**
      * @dataProvider providerWEEKDAY
-     * @group fail19
      */
     public function testWEEKDAY()
     {
-        $this->markTestIncomplete('TODO: This test should be fixed');
-
         $args = func_get_args();
         $expectedResult = array_pop($args);
         $result = call_user_func_array([DateTime::class, 'DAYOFWEEK'], $args);

tests/data/Calculation/DateTime/WEEKDAY.php

@@ -92,7 +92,7 @@ return [
     ],
     [
         '1900-2-1',
-        1,
+        4,
     ],
     [
         38093,