rocksdb: point the commit to the head of spdk-5.6.1

This was still pointing at the wrong place.

Change-Id: I793030432e9b4e7a4c284aa6c47273e9434cd4dc
Signed-off-by: Seth Howell <seth.howell@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/452245


Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>