There is the Twa, Mbuti and different groups in Central and West Africa. Then there are various other short black and brown people around the world. I would say "so-called 'pygmies'" to distance myself from the racist language of the euros dem, but there are more groups than just the Twa so sometimes you might have to say so-called 'pygmies' to clarify that you are talking about all these peoples and not only the Twa.