docs: fix fomatting

docs/source/optimizers.rst

@@ -20,6 +20,7 @@ Manual optimization
 ===================
 For advanced research topics like reinforcement learning, sparse coding, or GAN research, it may be desirable
 to manually manage the optimization process. To do so, do the following:
+
 * Disable automatic optimization in Trainer:  Trainer(automatic_optimization=False)
 * Drop or ignore the optimizer_idx argument
 * Use `self.manual_backward(loss)` instead of `loss.backward()` to automatically scale your loss