Update comment for NondeterministicFastCommit

Make it clearer that encoded slabs are still deterministic, so
array and map iterations will remain deterministic.

Only the sequence of changed slabs getting committed is
nondeterministic.

This is useful for migration programs that don't require
commit sequence of slabs to be deterministic while
still preserving deterministic encoding of slabs
(e.g. iteration of arrays and maps remain deterministic).

storage.go

@@ -969,8 +969,10 @@ func (s *PersistentSlabStorage) FastCommit(numWorkers int) error {
 	return nil
 }
 
-// NondeterministicFastCommit commits changes in nondeterministic order.
-// This is used by migration program when ordering isn't required.
+// NondeterministicFastCommit commits changed slabs in nondeterministic order.
+// Encoded slab data is deterministic (e.g. array and map iteration is deterministic).
+// IMPORTANT: This function is used by migration programs when commit order of slabs 
+// is not required to be deterministic (while preserving deterministic array and map iteration).
 func (s *PersistentSlabStorage) NondeterministicFastCommit(numWorkers int) error {
 	// No changes
 	if len(s.deltas) == 0 {