Move plateau schedulers epoch update to the training epoch loop (#8424)

pytorch_lightning/loops/epoch/training_epoch_loop.py

@@ -221,6 +221,8 @@ class TrainingEpochLoop(loops.Loop):
         self.trainer.call_hook('on_epoch_end')
         self.trainer.logger_connector.on_epoch_end()
 
+        self.update_lr_schedulers('epoch', update_plateau_schedulers=True)
+
         epoch_output = self._epoch_output
         # free memory
         self._epoch_output = None

pytorch_lightning/loops/fit_loop.py

@@ -233,8 +233,6 @@ class FitLoop(Loop):
         if self.epoch_loop.batches_seen == 0:
             return
 
-        self.epoch_loop.update_lr_schedulers('epoch', update_plateau_schedulers=True)
-
         did_train_only = not self.trainer.enable_validation or self.epoch_loop.val_loop.skip
         if did_train_only:
             self.global_step -= 1