Update on "[ET-VK] Tuning native layer norm local workgroup size to improve thread occupancy during reduce."

This diff is tuning the local workgroup size of the native layer norm operation in Vulkan backend of Executorch to improve thread occupancy during the reduce phase.

Differential Revision: [D72581293](https://our.internmc.facebook.com/intern/diff/D72581293/)

[ghstack-poisoned]

Author: trivedivivek