ns for fx: clean up duplicate code in get_matching_activations_a_shadows_b (#52927)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52927
Refactor to use an existing util instead of duplicating code, no logic
change.
Test Plan:
CI
Imported from OSS
Reviewed By: raghuramank100
Differential Revision: D26693474
fbshipit-source-id: 06b7047eb9a762557b7f679347e424c0dd009aad
