Changed function comment

Signed-off-by: Levi Harrison <git@leviharrison.dev>

promql/functions.go

@@ -629,7 +629,7 @@ func funcDeg(vals []parser.Value, args parser.Expressions, enh *EvalNodeHelper)
 	})
 }
 
-// === pi(Vector parser.ValueTypeVector) Vector ===
+// === pi() Scalar ===
 func funcPi(vals []parser.Value, args parser.Expressions, enh *EvalNodeHelper) Vector {
 	return Vector{Sample{Point: Point{
 		V: math.Pi,