alpine: update containerd to 1.4.6
alpine: update containerd to 1.4.6

As suggested on https://github.com/linuxkit/linuxkit/pull/3554#issuecomment-852910630

Signed-off-by: David Scott <bfcdf3e6ca6cef45543bfbb57509c92aec9a39fb@recoil.org>

furious-luke/linuxkit,JohnnyLeone/linuxkit,deitch/linuxkit,deitch/linuxkit,furious-luke/linuxkit,djs55/linuxkit,JohnnyLeone/linuxkit,djs55/linuxkit,deitch/linuxkit,JohnnyLeone/linuxkit,JohnnyLeone/linuxkit,linuxkit/linuxkit,JohnnyLeone/linuxkit,furious-luke/linuxkit,djs55/linuxkit,furious-luke/linuxkit,linuxkit/linuxkit,rn/linuxkit,rn/linuxkit,linuxkit/linuxkit,rn/linuxkit,linuxkit/linuxkit,deitch/linuxkit,deitch/linuxkit,djs55/linuxkit,djs55/linuxkit,linuxkit/linuxkit,furious-luke/linuxkit,rn/linuxkit,rn/linuxkit