Add missing ordinal test for 'th' suffix

Co-authored-by: Greg Korba <wirone@gmail.com>

tests/Feature/NumberTest.php

@@ -61,6 +61,7 @@
     $this->assertSame('1st', Number::ordinal(1));
     $this->assertSame('2nd', Number::ordinal(2));
     $this->assertSame('3rd', Number::ordinal(3));
+    $this->assertSame('4th', Number::ordinal(4));
 });
 
 it('converts numbers to percentages', function () {