vendor: bump runtime-spec to 5684b8af48c1

Update runtime-spec to get Intel RDT/MBA Linux configs which will be
used in successive commits.

Signed-off-by: Xiaochen Shen <xiaochen.shen@intel.com>

Author: xiaochenshen

vendor.conf

@@ -1,7 +1,7 @@
 # OCI runtime-spec. When updating this, make sure you use a version tag rather
 # than a commit ID so it's much more obvious what version of the spec we are
 # using.
-github.com/opencontainers/runtime-spec v1.0.0
+github.com/opencontainers/runtime-spec 5684b8af48c1ac3b1451fa499724e30e3c20a294
 # Core libcontainer functionality.
 github.com/mrunalp/fileutils ed869b029674c0e9ce4c0dfa781405c2d9946d08
 github.com/opencontainers/selinux v1.0.0-rc1