By Frank Dalleres Mercedes Formula 1 boss Toto Wolff has risked further riling Red Bull rival Christian Horner by admitting to ongoing talks with their world champion driver Max Verstappen. Verstappen has a contract with Red Bull until 2028 but has discussed a switch to Mercedes with Wolff this season amid turbulence at the Austrian-owned team. Horner appeared to take a swipe at Wolff after Sunday’s Dutch Grand Prix when he said he found it “surprising how much open discussion there is in the media about this topic”. The Mercedes principal has all but given up on luring Verstappen to replace F…