Fix more incompatibilities with Laravel 5.5

src/Database/DatabaseMigrationRepository.php

@@ -58,7 +58,8 @@ class DatabaseMigrationRepository implements MigrationRepositoryInterface
         return $this->table()
                 ->where('extension', $extension)
                 ->orderBy('migration', 'asc')
-                ->pluck('migration');
+                ->pluck('migration')
+                ->toArray();
     }
 
     /**