Prince Harry is set for a lads holiday with his “closest mates” as Meghan Markle stays home, it has been claimed. The Duke of Sussex is understood to head off on the lads’ trip after a private 40th birthday gathering with the family at the Sussexes’ Montecito mansion. Harry will “enjoy a weekend getaway with a few of his closest mates” to celebrate his milestone birthday, according to reports in The Sun. Meghan will stay behind in California with her children Archie, five, and Lilibet, three, who Harry previously said are the two “best gifts” he has ever received. Harry, who wrote his memoir S…