remove facter language override prevention hack

no longer needed since Celluloid 0.13.0 no longer uses Facter to determine CPU counts
we now require Celluloid >= 0.13.0

@justincampbell 
https://github.com/celluloid/celluloid/commit/568708d627d7bd1ece33c0b00a3f9ac6bf1e0c22
https://github.com/celluloid/celluloid/pull/164#issuecomment-13321498