SVN save code now and loaders are failing since the deployment of swh-loader-svn:1.8.9

Since the release and deployment of swh-loader-svn:1.8.9, the DumpMountAndLoadSvnRepository task type was removed: swh-loader-svn@0f1d1d54

It seems it's still used in production/staging environment by the save code now.

The result is all the svn save code now are failing:

{"asctime": "2023-11-21 17:21:54,109", "threadName": "MainThread", "pathname": "/opt/swh/.local/lib/python3.10/site-packages/celery/worker/consumer/consumer.py", "lineno": 587, "funcName": "on_unknown_task", "task_name": null, "task_id": null, "name": "celery.worker.consumer.consumer", "levelname": "ERROR", "message": "Received unregistered task of type 'swh.loader.svn.tasks.DumpMountAndLoadSvnRepository'.\nThe message has been ignored and discarded.\n\nDid you remember to import the module containing this task?\nOr maybe you're using relative imports?\n\nPlease see\nhttps://docs.celeryq.dev/en/latest/internals/protocol.html\nfor more information.\n\nThe full contents of the message body was:\n'[[], {\"url\": \"https://svn.code.sf.net/p/freeorion/code\"}, {\"callbacks\": null, \"errbacks\": null, \"chain\": null, \"chord\": null}]' (126b)\n\nThe full contents of the message headers:\n{'lang': 'py', 'task': 'swh.loader.svn.tasks.DumpMountAndLoadSvnRepository', 'id': '516a6766-91d7-47de-82d3-e02d742b58e1', 'shadow': None, 'eta': None, 'expires': None, 'group': None, 'group_index': None, 'retries': 0, 'timelimit': [None, None], 'root_id': '516a6766-91d7-47de-82d3-e02d742b58e1', 'parent_id': None, 'argsrepr': '()', 'kwargsrepr': \"{'url': 'https://svn.code.sf.net/p/freeorion/code'}\", 'origin': 'gen1@scheduler-runner-priority-ff7c85576-j24hv', 'ignore_result': False, 'replaced_task_nesting': 0, 'stamped_headers': None, 'stamps': {}}\n\nThe delivery info for this task is:\n{'consumer_tag': 'None12', 'delivery_tag': 5, 'redelivered': False, 'exchange': '', 'routing_key': 'save_code_now:swh.loader.svn.tasks.DumpMountAndLoadSvnRepository'}\n", "exc_info": "Traceback (most recent call last):\n  File \"/opt/swh/.local/lib/python3.10/site-packages/celery/worker/consumer/consumer.py\", line 658, in on_task_received\n    strategy = strategies[type_]\nKeyError: 'swh.loader.svn.tasks.DumpMountAndLoadSvnRepository'"}