That's a pretty common myth spread by articles like this one[0]. Wikipedia's article on Cysteine debunks it[1]:
The majority of L-cysteine is obtained industrially by hydrolysis of animal materials, such as poultry feathers or hog hair. Despite widespread belief otherwise, there is little evidence that human hair is used as a source material and its use is explicitly banned in the European Union.
Makes sense too, since ~50 billion chickens are slaughtered per year, the amount of poultry feathers available for processing probably dwarfs the amount of human available.
[0] http://www.naturalnews.com/032718_L-cysteine_commercial_brea...