Fix type to assert group size (pytorch#682)

Summary:
X-link: pytorch#3601

Pull Request resolved: facebookresearch/FBGEMM#682

Fix type to assert group size

Reviewed By: jianyuh

Differential Revision: D68499555

fbshipit-source-id: 58ac6869189924610d03ae7339ca3d24b1898fed

Author: Robert Luo

fbgemm_gpu/fbgemm_gpu/quantize_comm.py

@@ -241,7 +241,7 @@ def calc_quantized_size(
                 group_size = MX_GROUP_SIZE_DEFAULT
             assert (
                 input_len % group_size == 0
-            ), f"input_len {input_len} needs to be multiple of group_size 32"
+            ), f"input_len {input_len} needs to be multiple of group_size {group_size}"
             # quantized output size = half input size + number of groups (shared exp)
             ctx = none_throws(ctx)
             return (input_len // 2) + (input_len // ctx.mx_group_size)