Passengers aboard a flight Monday night landed safely at Newark Liberty International Airport after an unspecified threat was found written on the plane’s bathroom mirror, officials said. The threat was not credible, officials said. “Our pilots and law enforcement followed the regular procedure for this type of occurrence, which included having customers deplane a short distance from the terminal,” a United Airlines spokesperson told NJ Advance Media. The spokesperson said the plane, which had flown from London, will be swept by security teams and that connecting customers were expected to be …