[llvm] [AMDGPU] Remove unused amdgpu-disable-structurizer flag (PR #105800)

[Sameer Sahasrabuddhe via llvm-commits]

https://github.com/ssahasra approved this pull request.

Thank you! That option was my mess and I forgot to clean it up!

https://github.com/llvm/llvm-project/pull/105800