Don't log when failing to request TxIds when the protocol is shutting down

[agaffney]

Detect this specific error and get rid of these annoying log messages when the connection is closed by the remote node.

{"time":"2025-07-16T05:36:06.221048739Z","level":"ERROR","msg":"failed to get TxIds: protocol is shutting down","component":"network","protocol":"tx-submission","role":"server","connection_id":"172.18.0.7:3001<->172.18.0.9:3001"}