Convicted child killer Tanner Horner will spend the rest of his life at one of the most brutal death row prisons after being sentenced to die by a Texas jury this week. Horner will rot away at the Polunsky Unit, an infamously restrictive prison outside Houston where the state’s death row inmates are housed in an all-solitary confinement wing and spend at least 22 hours a day in their 60 square-foot cells. The former FedEx deliveryman, 34, was booked at the notorious prison Tuesday within hours of being sentenced for the gruesome murder of Athena Strand, 7, who he admitted to strangling to death while delivering a Christmas gift to her home in November 2022. Tanner Horner, 34, showed zero emotion as he learned his fate. AP Horner will remain at the prison until he dies by lethal injection — which could range anywhere from years to decades from now depending on how long he fights for appeal.…