Revert "Arm backend: Add PTE diff stage to Arm test pipeline" (pytorch#23320)

Reverts pytorch#23179

Many internal buck failures:

* buck2 test
fbcode//executorch/backends/arm/test:insert_data_layout_casts_pass --
--list-only
* buck2 test
fbcode//executorch/backends/arm/test:unsqueeze_before_repeat_pass --
--list-only
etc


```
    from executorch.backends.arm.test.tester.pte_diff_utils import (
../buck-out/v2/art/fbcode/fefbf0ce7e28db2b/executorch/backends/arm/test/__insert_data_layout_casts_pass__/insert_data_layout_casts_pass#link-tree/executorch/backends/arm/test/tester/pte_diff_utils.py:12: in <module>
    from executorch.devtools.pte_tool.diff_pte import PTEDiffResult
E   ModuleNotFoundError: No module named 'executorch.devtools.pte_tool'
```

```
tree/executorch/backends/arm/test/tester/pte_diff_utils.py", line 12, in <module>
    from executorch.devtools.pte_tool.diff_pte import PTEDiffResult
```


cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils
@Sebastian-Larsson @robell @rascani

Author: metascroy