Rename opt_idx to optimizer_idx in docs for complex training loops (#5712)

Author: creafz

README.md

@@ -223,7 +223,7 @@ with tempfile.NamedTemporaryFile(suffix='.onnx', delete=False) as tmpfile:
 
 ```python
 class LitAutoEncoder(pl.LightningModule):
-    def training_step(self, batch, batch_idx, opt_idx):
+    def training_step(self, batch, batch_idx, optimizer_idx):
         # access your optimizers with use_pl_optimizer=False. Default is True
         (opt_a, opt_b) = self.optimizers(use_pl_optimizer=True)
 

docs/source/starter/new-project.rst

@@ -268,7 +268,7 @@ Now you own the train loop!
 
 .. code-block:: python
 
-    def training_step(self, batch, batch_idx, opt_idx):
+    def training_step(self, batch, batch_idx, optimizer_idx):
         # access your optimizers with use_pl_optimizer=False. Default is True
         (opt_a, opt_b, opt_c) = self.optimizers(use_pl_optimizer=True)