test: remove failed test for deprecated Config class

1) CodeIgniter\Config\ConfigTest::testCreateNonConfig
ErrorException: Constant EVENT_PRIORITY_LOW already defined

/home/runner/work/CodeIgniter4/CodeIgniter4/app/Config/Constants.php:84
/home/runner/work/CodeIgniter4/CodeIgniter4/system/Config/Factories.php:271
/home/runner/work/CodeIgniter4/CodeIgniter4/system/Config/Factories.php:148
/home/runner/work/CodeIgniter4/CodeIgniter4/system/Config/Config.php:31
/home/runner/work/CodeIgniter4/CodeIgniter4/tests/system/Config/ConfigTest.php:51

Author: kenjis

tests/system/Config/ConfigTest.php

@@ -46,13 +46,6 @@ public function testCreateSharedInstance(): void
         $this->assertSame($Config2, $Config);
     }
 
-    public function testCreateNonConfig(): void
-    {
-        $Config = Config::get('Constants', false);
-
-        $this->assertNull($Config);
-    }
-
     /**
      * @runInSeparateProcess
      * @preserveGlobalState disabled