Add comments to min_partition

Summary:
As titled

Created from CodeHub with https://fburl.com/edit-in-codehub

Reviewed By: sarckk

Differential Revision: D54489049

fbshipit-source-id: 6365a8051d4d420b18dae702c8769a98ea15f38b

Author: gnahzg

torchrec/distributed/planner/types.py

@@ -429,7 +429,7 @@ class ParameterConstraints:
 
     sharding_types: Optional[List[str]] = None
     compute_kernels: Optional[List[str]] = None
-    min_partition: Optional[int] = None  # CW sharding
+    min_partition: Optional[int] = None  # CW sharding, min CW dim to shard
     pooling_factors: List[float] = field(
         default_factory=lambda: [POOLING_FACTOR]
     )  # average number of embedding lookups required per sample