Mask2Former _init_weights

### System Info - `transformers` version: 4.45.2 - Platform: Linux-6.8.0-51-generic-x86_64-with-glibc2.39 - Python version: 3.11.9 - Huggingface_hub version: 0.24.6 - Safetensors version: 0.4.4 - Accelerate version: not installed - Accelerate config: not found - PyTorch version (GPU?): 2.4.0+cu121 (True) - Tensorflow version (GPU?): not installed (NA) - Flax version (CPU?/GPU?/TPU?): not installed (NA) - Jax version: not installed - JaxLib version: not installed - Using distributed or parallel set-up in script?: no - Using GPU in script?: yes - GPU type: NVIDIA RTX A6000 ### Who can help? _No response_ ### Information - [ ] The official example scripts - [ ] My own modified scripts ### Tasks - [ ] An officially supported task in the `examples` folder (such as GLUE/SQuAD, ...) - [ ] My own task or dataset (give details below) ### Reproduction Run _init_weights ### Expected behavior The _init_weights method of Mask2Former has multiple problems. It initializes nn.Embeddings with an std of .02 (original Mask2Former code uses PyTorch's default init with std of 1.0). Similarly, the mask MLP is initialised wrongly with zero biases. Finally, another example of a problem is that the initialisation of the multi-scale deformable attention is overwritten by the branch for the Mask2FormerPixelDecoderEncoderOnly.