[iOS][GPU] Fix the clamp shader function for x86_64 (#63062)

[iOS][GPU] Fix the clamp shader function for x86_64 (#63062)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63062

Pervasively, due to the need of supporting 10.0, we used a fp16 version of the clamp kernel on Metal, which didn't work well on x86_64. Since we don't need to support 10.0 anymore, we can use the fp32 version, which works both on arm64 and x86_64.
ghstack-source-id: 135536785

Test Plan:
- `buck test pp-macos`
- Op tests in the playground app

{F641013793}

Reviewed By: husthyc

Differential Revision: D30239931

fbshipit-source-id: 6ad1bf71422b537e052fbd7b7465ba8deb7ca0cf