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/deformable_detr/test_modeling_deformable_detr.py

@@ -564,10 +564,6 @@ class DeformableDetrModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineT
                         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
-
     def test_two_stage_training(self):
         model_class = DeformableDetrForObjectDetection
         config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()