A high point of Sundance’s annual party circuit — Cinetic’s Monday night bash at Zoom on Main Street — is apparently off. Insiders tell me that unless a last-minute sponsor comes forward, the party “likely” won’t be held. Sad, because it regularly brought out Sundance Film Festival heavy hitters while head John Sloss held impromptu meetings with distribution heads upstairs. It was a standing-room-only affair with crowds packing the sidewalk and waiting to get in. The end of an era…