chore: fix comment (#20498)

Signed-off-by: VitalikButerinEth <csyingyu@126.com>

x/auth/vesting/types/period.go

@@ -31,7 +31,7 @@ func (p Periods) TotalDuration() time.Duration {
 	return time.Duration(len) * time.Second
 }
 
-// TotalDuration returns the sum of coins for the period
+// TotalAmount returns the sum of coins for the period
 func (p Periods) TotalAmount() sdk.Coins {
 	total := sdk.Coins{}
 	for _, period := range p {