Fix spelling and holt-winters check (#4424)

Signed-off-by: Benjamin Raskin <braskin@uber.com>

promql/functions.go

@@ -232,10 +232,10 @@ func funcHoltWinters(vals []Value, args Expressions, enh *EvalNodeHelper) Vector
 
 	// Sanity check the input.
 	if sf <= 0 || sf >= 1 {
-		panic(fmt.Errorf("invalid smoothing factor. Expected: 0 < sf < 1 goT: %f", sf))
+		panic(fmt.Errorf("invalid smoothing factor. Expected: 0 < sf < 1, got: %f", sf))
 	}
 	if tf <= 0 || tf >= 1 {
-		panic(fmt.Errorf("invalid trend factor. Expected: 0 < tf < 1 goT: %f", sf))
+		panic(fmt.Errorf("invalid trend factor. Expected: 0 < tf < 1, got: %f", tf))
 	}
 
 	var l int