[ref] conf: ModulePriority remove () on unit variants

doc/en/dev/developing-a-durs-module.md

doc/fr/developpeurs/developper-un-module-durs.md

lib/core/module/src/lib.rs

lib/modules/gva/src/lib.rs

lib/modules/skeleton/lib.rs

lib/modules/tui/tui.rs

lib/modules/ws2p-v1-legacy/src/lib.rs

lib/modules/ws2p/ws2p/src/lib.rs