Remove manopt + grad clipping (by @flukeskywalker)

Author: akihironitta

pytorch_lightning/core/lightning.py

@@ -1208,9 +1208,6 @@ def manual_backward(self, loss: Tensor, optimizer: Optional[Optimizer] = None, *
 
         See :ref:`manual optimization<common/optimizers:Manual optimization>` for more examples.
 
-        .. tip::
-            In manual mode, we still automatically clip grads if ``Trainer(gradient_clip_val=x)`` is set.
-
         Example::
 
             def training_step(...):