luci-app-lxc: remove obsolete note about enabling kernel features
luci-app-lxc: remove obsolete note about enabling kernel features

Since commit openwrt/openwrt@fcb41decf6 ("config: enable some useful
features on !SMALL_FLASH devices") LXC related features are enabled by
default.
Hence remove note stating that a custom image is required for LXC.

Signed-off-by: Daniel Golle <3d0f3b9ddcacec30c4008c5e030e6c13a478cb4f@makrotopia.org>

tobiaswaldvogel/luci,rogerpueyo/luci,nmav/luci,nmav/luci,nmav/luci,openwrt/luci,lbthomsen/openwrt-luci,tobiaswaldvogel/luci,nmav/luci,hnyman/luci,openwrt/luci,rogerpueyo/luci,openwrt/luci,tobiaswaldvogel/luci,nmav/luci,lbthomsen/openwrt-luci,lbthomsen/openwrt-luci,rogerpueyo/luci,nmav/luci,hnyman/luci,rogerpueyo/luci,openwrt/luci,lbthomsen/openwrt-luci,openwrt/luci,hnyman/luci,rogerpueyo/luci,rogerpueyo/luci,hnyman/luci,openwrt/luci,openwrt/luci,rogerpueyo/luci,hnyman/luci,tobiaswaldvogel/luci,openwrt/luci,tobiaswaldvogel/luci,rogerpueyo/luci,nmav/luci,lbthomsen/openwrt-luci,hnyman/luci,hnyman/luci,tobiaswaldvogel/luci,nmav/luci,nmav/luci,tobiaswaldvogel/luci,lbthomsen/openwrt-luci,lbthomsen/openwrt-luci,hnyman/luci,lbthomsen/openwrt-luci,tobiaswaldvogel/luci