For years now, there have been rumblings about “Lethal Weapon 5.” With “Beverly Hills Cop” getting a new sequel, and other franchises from the ‘80s and ‘90s coming back for “one last” romp, it was only a matter of time that one of the most famous buddy-cop franchises would be revived, even if it’s been 22 years since the fourth feature. But according to filmmaker Richard Donner, not only is “Lethal Weapon 5” happening, but it’s also the end of the franchise.