remove Heap.Update() call when setting Proposer field

In for loop of IncrementAccum(), Heap.Update() call is unnecessary when i == times - 1.

types/validator_set.go

@@ -60,13 +60,14 @@ func (valSet *ValidatorSet) IncrementAccum(times int) {
 	// Decrement the validator with most accum times times
 	for i := 0; i < times; i++ {
 		mostest := validatorsHeap.Peek().(*Validator)
+		// mind underflow
+		mostest.Accum = safeSubClip(mostest.Accum, valSet.TotalVotingPower())
+
 		if i == times-1 {
 			valSet.Proposer = mostest
+		} else {
+			validatorsHeap.Update(mostest, accumComparable{mostest})
 		}
-
-		// mind underflow
-		mostest.Accum = safeSubClip(mostest.Accum, valSet.TotalVotingPower())
-		validatorsHeap.Update(mostest, accumComparable{mostest})
 	}
 }