Update lr_schedules.py (#4563)
add cosine annealing scheduler
this scheduler is widely used in image classification task, and many llm
(e.g. llama) use this also.
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Co-authored-by: Olatunji Ruwase <olruwase@microsoft.com>
Co-authored-by: Logan Adams <114770087+loadams@users.noreply.github.com>
