Fix some typos in the docs (#14126)

* Fix some typos in the docs

* Fix a styling issue

* Fix code quality check error

docs/source/training.rst

@@ -335,7 +335,7 @@ scheduler. The default optimizer used by the :class:`~transformers.Trainer` is :
 
     optimizer = AdamW(model.parameters(), lr=5e-5)
 
-Finally, the learning rate scheduler used by default it just a linear decay form the maximum value (5e-5 here) to 0:
+Finally, the learning rate scheduler used by default is just a linear decay from the maximum value (5e-5 here) to 0:
 
 .. code-block:: python