Revert low cpu mem tie weights (#29135)

* Revert "Add tie_weights() to LM heads and set bias in set_output_embeddings() (#28948)"

This reverts commit 725f4ad1cc.

* Revert "Patch to skip failing `test_save_load_low_cpu_mem_usage` tests (#29043)"

This reverts commit 4156f517ce.

tests/models/marian/test_modeling_marian.py

@@ -372,12 +372,6 @@ class MarianModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMix
     def test_training_gradient_checkpointing_use_reentrant_false(self):
         pass
 
-    @unittest.skip(
-        "Not currently compatible. Fails with - NotImplementedError: Cannot copy out of meta tensor; no data!"
-    )
-    def test_save_load_low_cpu_mem_usage(self):
-        pass
-
 
 def assert_tensors_close(a, b, atol=1e-12, prefix=""):
     """If tensors have different shapes, different values or a and b are not both tensors, raise a nice Assertion error."""