[DataPipe] Adding a note about FileLister behavior (#72619)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/72619
Adding a note. See Vitaly's comment here: https://github.com/pytorch/pytorch/pull/70602#discussion_r803025044
Test Plan: Imported from OSS
Reviewed By: VitalyFedyunin
Differential Revision: D34119517
Pulled By: NivekT
fbshipit-source-id: e033817d63498ae480e854701d7fdd4ebc9dfb56
(cherry picked from commit 6bb1c0087b5ccf72351be9535305797241463a6f)
