Fix challange counts

Signed-off-by: Jakub Sztandera <kubuxu@protocol.ai>

params_shared.go

@@ -9,10 +9,10 @@ const SectorChallengeRatioDiv = 25
 const MaxFallbackPostChallengeCount = 10
 
 // extracted from lotus/chain/types/blockheader
-func ElectionPostChallengeCount(sectors uint64, faults int) uint64 {
-	if sectors == 0 {
+func ElectionPostChallengeCount(sectors uint64, faults uint64) uint64 {
+	if sectors-faults == 0 {
 		return 0
 	}
 	// ceil(sectors / SectorChallengeRatioDiv)
-	return (sectors-uint64(faults)-1)/SectorChallengeRatioDiv + 1
+	return (sectors-faults-1)/SectorChallengeRatioDiv + 1
 }