up until 6.05.03 Ranger Archetype "Beast Master" was OK (removed the 6th level Combat Style Feat), but 6.05.04+ remove 2 feats instead of 1.
APG p.124-125: replace standard ranger class skill; replace hunter's bond, replace 6th level combat style feat; replace camouflage.
Up to 6.05.03 Ranger 6 has 2 combat style feats, and the Beast Master reduces that to 1 CSF.
in 6.05.04 Ranger 6 has 2 Combat Style Feats, but if you add the Archetype, both disappear.
Pathfinder Core Supplements rule-set (probably just APG)