fix_combine_two_partition_size (#47053)
Summary:
fix combine_two_partitions in Partitioner.py to calculate new partition used memory size after combining two partitions.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47053
Reviewed By: gcatron
Differential Revision: D24624270
Pulled By: scottxu0730
fbshipit-source-id: a0e2a8486e012d02ea797d6ba36ab304d27cc93f
