Clarify the need to add `use_peers` option to RPC `work_generate` calls on work generation guide

[zhyatt]

Currently only mentioned in https://docs.nano.org/integration-guides/work-generation/#pre-caching section but probably should be clarified elsewhere.

[zhyatt]

May be unnecessary depending on how work generation shifts with election prioritization changes. Moving to V23.0 for further consideration.