fix cosine scheduler docstring

Summary: as title

Reviewed By: myleott

Differential Revision: D16773845

fbshipit-source-id: 2d10e197c31f94d894430559327289a4d03e33f7

fairseq/optim/lr_scheduler/cosine_lr_scheduler.py

@@ -16,7 +16,7 @@ class CosineSchedule(FairseqLRScheduler):
 
     We also support a warmup phase where we linearly increase the learning rate
     from some initial learning rate (``--warmup-init-lr``) until the configured
-    learning rate (``--lr``).
+    max learning rate (``--max-lr``).
 
     During warmup::