Update MD5 checkum values of FSDP consolidated shards

[tangbinh]

Summary of Changes
As mentioned in #590, the recent changes to the FSDP resharding script (see #459) alter the MD5 checksum values when we run it with the options --skip-optimizer-state True and --unflatten-weights True. We update the doc to be consistent with those changes.

Test Plan
The new checksum values are computed using the following command:

for j in {0..7}; do md5sum /data/checkpoints/opt-175b/reshard_no_os_unflat/reshard-model_part-$j.pt; done