This claim - that we're certainly not living in a computer simulation - is premature at best. What @masterthematrix, @lukestokes, and @tabzjones have said hits the mark.

Unless we've somehow mapped the domain of all that will ever be known or possible, to rule out a simulation theory so concretely is pretty absurd. I don't know what the person who wrote that article in Cosmos was trying to achieve - the title alone is click-bait-y, so I don't know that the objective was to be thorough. Not to mention that there is inconsistency in the content: the caption below the article's image says some physical phenomenon "may" be impossible to simulate, while elsewhere he says that such simulation is impossible, both practically and in principle.

It's quite arrogant to think we know where the boundaries of what is possible or, well, the boundaries of what can be are with complete certainty.