Set checkpoint_dir default to empty

Signed-off-by: Kunjan Patel <kunjan@ucla.edu>

Author: coolkp

src/maxdiffusion/configs/base_wan_14b.yml

@@ -198,7 +198,7 @@ remat_policy: "NONE"
 
 # checkpoint every number of samples, -1 means don't checkpoint.
 checkpoint_every: -1
-checkpoint_dir: "/mnt/disks/kunjanp-dev/output-dir/test-wan-training-new/checkpoints"
+checkpoint_dir: ""
 # enables one replica to read the ckpt then broadcast to the rest
 enable_single_replica_ckpt_restoring: False