Fix discrete sampler test to correctly run Chi2 test (#73251)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/73251
Scipy's chisquare test requires that the observed frequencies should sum up to the same number as the expected frequences. This modifies `_check_sampler_discrete` to ensure that two match. See: https://github.com/scipy/scipy/issues/12282 for details.
Test Plan: Unit tests pass on platform010
Reviewed By: r-barnes
Differential Revision: D34402314
fbshipit-source-id: 995b4ddf668cfb551176d3bd21fb8415dfe96cc1
(cherry picked from commit d81a133b0d2cdc621d08caf31afd69d716229b97)
