Split only the necessary number of values.

As suggested by @pellared. Good suggestion, that.

Co-authored-by: Robert Pająk <pellared@hotmail.com>

semconv/v1.4.0/http.go

@@ -225,7 +225,7 @@ func HTTPServerAttributesFromHTTPRequest(serverName, route string, request *http
 		attrs = append(attrs, HTTPRouteKey.String(route))
 	}
 	if values, ok := request.Header["X-Forwarded-For"]; ok && len(values) > 0 {
-		if addresses := strings.Split(values[0], ","); len(addresses) > 0 {
+		if addresses := strings.SplitN(values[0], ",", 2); len(addresses) > 0 {
 			attrs = append(attrs, HTTPClientIPKey.String(addresses[0]))
 		}
 	}