Sean Connery, the best known member of the cast for Terry Gilliam's "The Adventures of Baron Munchausen," has reportedly withdrawn from the over-budget film because the sequence in which he was to have appeared was dramatically trimmed in recent cost-saving script changes. Connery, who played a cameo role in Gilliam's popular "Time Bandits," could not be reached for comment, but sources close to the Rome-based production confirmed that the actor pulled out after a lengthy sequence--and his role in it--were pared down. "Munchausen," an epic fantasy originally budgeted at $23.5 million, was shut down for two weeks last month by the film's completion guarantors in order to get the budget under control. Estimates of the budget overage have run as high as $10 million. Besides Connery, the cast includes Oliver Reed, Jonathan Pryce, Eric Idle and Katherine Helmond with British stage veteran John Neville playing the title role. Executives at Columbia Pictures, the world-wide distributor of "Munchausen," were shown about 60 minutes of footage from the film Friday. A spokesman for the studio said Columbia's new president, Dawn Steel, was pleased with what she had seen.