How do you "shear" a snow golem's face?
Solution 1:
As of Minecraft PC 1.9 snapshot 15w49a Shearing snow golems' pumpkin is no longer exclusive to minecraft PE. With this snapshot players can now shear snow golem's pumpkin by right clicking on them with shears.
Solution 2:
It can only be done in the pocket edition. If you look at the Minecraft Wiki for snow golems, you'll see under the change log for the Pocket Edition:
Snow golems' pumpkin can now be removed with shears. This is version exclusive.