Make sure COMPOSER_AUTOLOADER_PATH is always declared

Sacrifice dynamic composer autoloader path to do this, because we don't
need it anyway - it was a misconceived feature from the days when I used
the same workspace for PM3 and PM4 both.

src/CoreConstants.php

@@ -35,3 +35,4 @@ define('pocketmine\_CORE_CONSTANTS_INCLUDED', true);
 
 define('pocketmine\PATH', dirname(__DIR__) . '/');
 define('pocketmine\RESOURCE_PATH', dirname(__DIR__) . '/resources/');
+define('pocketmine\COMPOSER_AUTOLOADER_PATH', dirname(__DIR__) . '/vendor/autoload.php');