[ticket/12963] Revert back to "migrations" folder name for extensions

The issues that can be created with the name change are just too much

PHPBB3-12963

phpBB/phpbb/console/command/db/migrate.php

@@ -117,17 +117,9 @@ class migrate extends \phpbb\console\command\command
 		$migrations = $this->extension_manager
 			->get_finder()
 			->core_path('phpbb/db/migration/data/')
-			->extension_directory('/migration')
-			->get_classes();
-
-		// @deprecated 3.1.0-RC4 (To be removed: 3.2.0)
-		$migrations_deprecated = $this->extension_manager
-			->get_finder()
 			->extension_directory('/migrations')
 			->get_classes();
 
-		$migrations = array_merge($migrations, $migrations_deprecated);
-
 		$this->migrator->set_migrations($migrations);
 	}