It likely originates from the "I ❤ NY" advertising campaign in the late 70s to promote New York as a tourist destination.
It was very popular as a t-shirt design, set out like this.
Image & article - WIkipedia - I Love New York
It's supposed to be pronounced as "I Love New York" but increasingly became parodied as, "I heart New York" and there was even a movie in 2004 called "I Heart Huckabees",
"i ❤ huckabees" was used as the 'logo' title, but IMDB & Wikipedia both spell it out as 'heart' rather than 'love'.
So it means, Cheney still loves waterboarding*
*Waterboarding is a form of torture in which water is poured over a cloth covering the face and breathing passages of an immobilized captive, causing the person to experience the sensation of drowning.