added GPTNeoForTokenClassification (#22908)

* added GPTNeoForTokenClassification

* add to top-level init

* fixup

* test

* more fixup

* add to gpt_neo.mdx

* repo consistency

* dummy copy

* fix copies

* optax >= 0.1.5 assumes jax.Array exists - which it doesn't for jax <= 0.3.6

* merge with main made this superfluous

* added classifier_dropout

* remove legacy code

* removed fmt:on/off
removed expected_outputs

* doc style fix

* classifier_dropout is always in config

---------

Co-authored-by: Prof. Peter Schneider-Kamp <jps@ordbogen.com>

docs/source/en/model_doc/gpt_neo.mdx

@@ -74,6 +74,11 @@ The `generate()` method can be used to generate text using GPT Neo model.
 [[autodoc]] GPTNeoForSequenceClassification
     - forward
 
+## GPTNeoForTokenClassification
+
+[[autodoc]] GPTNeoForTokenClassification
+    - forward
+
 ## FlaxGPTNeoModel
 
 [[autodoc]] FlaxGPTNeoModel