Deprecate TransfoXL (#27607)

* fix

* fix

* trigger

* Apply suggestions from code review

Co-authored-by: Lysandre Debut <hi@lysand.re>

* tic

* revert

* revert

---------

Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>
Co-authored-by: Lysandre Debut <hi@lysand.re>

tests/test_modeling_common.py

@@ -1927,7 +1927,6 @@ class ModelTesterMixin:
             "FunnelForPreTraining",
             "ElectraForPreTraining",
             "XLMWithLMHeadModel",
-            "TransfoXLLMHeadModel",
         ]:
             for k in key_differences:
                 if k in ["loss", "losses"]: