change asan test shard to 3 (#69843)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/68261
This PR changes the number of test shard from 2-->3 for all Asan test, aiming to improve the run time for Asan tests.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69843
Reviewed By: janeyx99
Differential Revision: D33160771
Pulled By: xidachen
fbshipit-source-id: dba1d318cc49b923e18704839471d8753cc00eca
