docs: Update limitations page to mention support for VFIO.
docs: Update limitations page to mention support for VFIO.

The latest virtcontainers library supports passing devices
to the VM with VFIO passthrough.
Update limitations to reflect this.

Fixes #713

Signed-off-by: Archana Shinde <047ac45ce396f63f3cf93ff43725668e736e0632@intel.com>

devimc/runtime,clearcontainers/runtime,chavafg/runtime,devimc/runtime,clearcontainers/runtime,chavafg/runtime