Remove proprietary license (pytorch#9389)

### Summary
- Removed MTK proprietary header: NeauronAdapter.h from repo. Need to be
downloaded from NeuroPilot Express SDK.\
- Modify license declaration in multiple header.

Fix pytorch#9279

---------

Co-authored-by: Poyuan Jeng <[email protected]>

Author: 2 people

backends/mediatek/README.md

@@ -37,6 +37,7 @@ Download [NeuroPilot Express SDK](https://neuropilot.mediatek.com/resources/publ
 - `libneuron_buffer_allocator.so`: This utility library is designed for allocating DMA buffers necessary for model inference.
 - `mtk_converter-8.8.0.dev20240723+public.d1467db9-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl`: This library preprocess the model into a MediaTek representation.
 - `mtk_neuron-8.2.2-py3-none-linux_x86_64.whl`: This library converts the model to binaries.
+- Copy `NeuronAdapter.h` under `backends/mediatek/runtime/include/api/`.
 
 ### Setup
 
@@ -76,4 +77,4 @@ Follow the steps below to setup your build environment:
    export LD_LIBRARY_PATH=<path_to_usdk>:<path_to_neuron_backend>:$LD_LIBRARY_PATH
    ```
 
-Please refer to `executorch/examples/mediatek/` for export and execution examples of various of models.
+Please refer to `executorch/examples/mediatek/` for export and execution examples of various of models.