ENGCOM-3609: Fixed fatal error if upgrading from Magento v2.0.0 to v2.3 and non system attributes missing #19530

 - Merge Pull Request #19530 from suneet64/magento2:configurable-product-attribute-fix
 - Merged commits:
   1. eb05687
   2. 861fd86

Author: magento-engcom-team

app/code/Magento/ConfigurableProduct/Setup/Patch/Data/InstallInitialConfigurableAttributes.php

@@ -6,16 +6,16 @@
 
 namespace Magento\ConfigurableProduct\Setup\Patch\Data;
 
+use Magento\ConfigurableProduct\Model\Product\Type\Configurable;
 use Magento\Eav\Setup\EavSetup;
 use Magento\Eav\Setup\EavSetupFactory;
-use Magento\Framework\App\ResourceConnection;
 use Magento\Framework\Setup\ModuleDataSetupInterface;
 use Magento\Framework\Setup\Patch\DataPatchInterface;
 use Magento\Framework\Setup\Patch\PatchVersionInterface;
-use Magento\ConfigurableProduct\Model\Product\Type\Configurable;
 
 /**
  * Class InstallInitialConfigurableAttributes
+ *
  * @package Magento\ConfigurableProduct\Setup\Patch
  */
 class InstallInitialConfigurableAttributes implements DataPatchInterface, PatchVersionInterface
@@ -24,6 +24,7 @@ class InstallInitialConfigurableAttributes implements DataPatchInterface, PatchV
      * @var ModuleDataSetupInterface
      */
     private $moduleDataSetup;
+
     /**
      * @var EavSetupFactory
      */
@@ -43,7 +44,7 @@ public function __construct(
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public function apply()
     {
@@ -84,23 +85,23 @@ public function apply()
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public static function getDependencies()
     {
         return [];
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public static function getVersion()
     {
         return '2.0.0';
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public function getAliases()
     {