Simplify string concat example in math.Add

content/en/functions/math/Add.md

@@ -26,10 +26,5 @@ If one of the numbers is a [`float`], the result is a `float`.
 You can also use the `add` function to concatenate strings.
 
 ```go-html-template
-{{ $s := slice "h" "u" "g" "o" }}
-{{ $t := "" }}
-{{ range $s }}
-  {{ $t = add $t . }}
-{{ end }}
-{{ $t }} → hugo
+{{ add "hu" "go" }} → hugo
 ```