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/deta/test_modeling_deta.py

@@ -520,10 +520,6 @@ class DetaModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMixin
                         msg=f"Parameter {name} of model {model_class} seems not properly initialized",
                     )
 
-    @unittest.skip("Cannot be initialized on meta device as some weights are modified during the initialization")
-    def test_save_load_low_cpu_mem_usage(self):
-        pass
-
 
 TOLERANCE = 1e-4