remove Unused parameter 'sf' in calcTrendValue function (#6900)

Signed-off-by: fuling <fuling.lgz@alibaba-inc.com>

promql/functions.go

@@ -193,10 +193,11 @@ func instantValue(vals []parser.Value, out Vector, isRate bool) Vector {
 
 // Calculate the trend value at the given index i in raw data d.
 // This is somewhat analogous to the slope of the trend at the given index.
-// The argument "s" is the set of computed smoothed values.
-// The argument "b" is the set of computed trend factors.
-// The argument "d" is the set of raw input values.
-func calcTrendValue(i int, sf, tf, s0, s1, b float64) float64 {
+// The argument "tf" is the trend factor.
+// The argument "s0" is the computed smoothed value.
+// The argument "s1" is the computed trend factor.
+// The argument "b" is the raw input value.
+func calcTrendValue(i int, tf, s0, s1, b float64) float64 {
 	if i == 0 {
 		return b
 	}
@@ -249,7 +250,7 @@ func funcHoltWinters(vals []parser.Value, args parser.Expressions, enh *EvalNode
 		x = sf * samples.Points[i].V
 
 		// Scale the last smoothed value with the trend at this point.
-		b = calcTrendValue(i-1, sf, tf, s0, s1, b)
+		b = calcTrendValue(i-1, tf, s0, s1, b)
 		y = (1 - sf) * (s1 + b)
 
 		s0, s1 = s1, x+y