Remove errnonoeous comma in logging call (#474)

pytorch_lightning/callbacks/pt_callbacks.py

@@ -253,7 +253,7 @@ class ModelCheckpoint(Callback):
                         if self.verbose > 0:
                             logging.info(
                                 f'\nEpoch {epoch + 1:05d}: {self.monitor} improved'
-                                f' from {self.best:0.5f} to {current:0.5f},',
+                                f' from {self.best:0.5f} to {current:0.5f},'
                                 f' saving model to {filepath}')
                         self.best = current
                         self.save_model(filepath, overwrite=True)