docs: pdp proof clock docs #2380

Job	Run time
ci-lint	20s
mod-tidy-check	42s
gofmt	19s
lint	4m 11s
build-debug	5m 5s
build-mainnet	5m 5s
gen-check	6m 44s
setup-params	7s
build-2k	4m 59s
build-calibnet	5m 13s
build-forest	5m 4s
test (test-itest-alertnow, ./itests/alertnow_test.go)	2m 38s
test (test-itest-harmonyDB, ./itests/harmonydb_test.go)	4m 20s
test (test-all, `go list ./... \| grep -v curio/itests`)	4m 9s
test (test-itest-curio, ./itests/curio_test.go)	4m 38s
	53m 34s

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