Standardize 2-space tabs in codegen (#4043)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/4043

for consistently with the non-generated ET-VK code.

The new perf codegen will build off this existing correctness codegen and I want the generated code to be readable.
ghstack-source-id: 231368098
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Reviewed By: copyrightly

Differential Revision: D58954596

fbshipit-source-id: 11fab7c2c8a3d426bcae143a6c5e5a99aa34a2ab