[vulkan] Fix concat op in feature dimension (#101721)
Summary: Fix a small bug in the `cat_feature` shader where an early exit path was not being taken correctly.
Test Plan:
Referring to [Pytorch Vulkan Testing Procedures](https://www.internalfb.com/intern/wiki/Pytorch_Vulkan_Backend/Development/Vulkan_Testing_Procedures/):
* Run operator unit tests on Mac and Android
* Run model inference and correctness benchmarks
Differential Revision: D45962806
Pull Request resolved: https://github.com/pytorch/pytorch/pull/101721
Approved by: https://github.com/salilsdesai
