rpc_api.md: rename .proc_enable_all_plugins -> .proc_before_online

Summary

• rpc_api.md: fix sorting
• rpc_api.md: rename .proc_enable_all_plugins -> .proc_before_online

25.2.0-4-g8dbc7434

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• Follow-up for picodata!1662 (merged)
• Staging:
  • https://docs.binary.picodata.io/picodata/asab_update_rpc_api/