[ExecuTorch] Arm Ethos: Disable pyre (#8746)

Disabling Pyre. Relying on OSS mypy enabled in #7776.

Differential Revision: [D70146769](https://our.internmc.facebook.com/intern/diff/D70146769/)

ghstack-source-id: 268178737
Pull Request resolved: https://github.com/pytorch/executorch/pull/8664

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Co-authored-by: Digant Desai <digantdesai@meta.com>