Remove outdated instructions from README
Remove outdated instructions from README

btrfs stuff now works fine on BOSH Lite

Pivotal-DataFabric/garden-linux-release,cloudfoundry-incubator/garden-linux-release,Pivotal-DataFabric/garden-linux-release,luan/garden-linux-release,cloudfoundry-incubator/garden-linux-release,cloudfoundry-incubator/garden-linux-release,Pivotal-DataFabric/garden-linux-release,cloudfoundry-incubator/garden-linux-release,Pivotal-DataFabric/garden-linux-release,luan/garden-linux-release,luan/garden-linux-release,cloudfoundry-incubator/garden-linux-release,luan/garden-linux-release