Feat/environment variables in workflow (#6515)

Co-authored-by: JzoNg <jzongcode@gmail.com>

api/schedule/clean_unused_datasets_task.py

@@ -15,7 +15,7 @@ from models.dataset import Dataset, DatasetQuery, Document
 @app.celery.task(queue='dataset')
 def clean_unused_datasets_task():
     click.echo(click.style('Start clean unused datasets indexes.', fg='green'))
-    clean_days = int(dify_config.CLEAN_DAY_SETTING)
+    clean_days = dify_config.CLEAN_DAY_SETTING
     start_at = time.perf_counter()
     thirty_days_ago = datetime.datetime.now() - datetime.timedelta(days=clean_days)
     page = 1