[NFC] Remove dangerous vestigial noise

[AlexVlx]

It is unclear what the code being removed was meant to do / fix, but it's lost any meaning with passage of time, and is a bug farm waiting to manifest.

[z1-cciauto]

PSDB Link: https://compiler-ci.amd.com/job/compiler-psdb-amd-staging/5808

[github-actions]

⚠️ SPIRV translator lit suite (check-amd-llvm-spirv): 22 failing — non-blocking (see run).

Upstream Khronos churn breaks these intermittently; check whether the failure is also on amd-staging tip before assuming this PR caused it.

Failing tests

LLVM_SPIRV :: constant/local-float-point-constants.ll
LLVM_SPIRV :: extensions/EXT/SPV_EXT_shader_atomic_float_/atomicrmw_fsub_half.ll
LLVM_SPIRV :: extensions/EXT/SPV_EXT_float8/conversions_matrix.ll
LLVM_SPIRV :: extensions/EXT/SPV_EXT_float8/conversions_scalar_vector.ll
LLVM_SPIRV :: extensions/INTEL/SPV_INTEL_float4/conversions_scalar_vector.ll
LLVM_SPIRV :: extensions/INTEL/SPV_INTEL_float4/conversions_packed.ll
LLVM_SPIRV :: extensions/INTEL/SPV_INTEL_fp_conversions/spv_intel_fp_conversions.ll
LLVM_SPIRV :: extensions/INTEL/SPV_INTEL_int4/conversions_packed.ll
LLVM_SPIRV :: extensions/INTEL/SPV_INTEL_sigmoid/sigmoid_f16.ll
LLVM_SPIRV :: extensions/KHR/SPV_KHR_bfloat16/cooperative_matrix_bfloat16.ll
LLVM_SPIRV :: extensions/KHR/SPV_KHR_cooperative_matrix/conversion_instructions.ll
LLVM_SPIRV :: extensions/KHR/SPV_KHR_uniform_group_instructions/group-instructions.ll
LLVM_SPIRV :: llvm-intrinsics/amdgcn-intrinsic-addrspace.ll
LLVM_SPIRV :: extensions/KHR/SPV_KHR_subgroup_rotate/SPV_KHR_subgroup_rotate.cl
LLVM_SPIRV :: transcoding/OpImageSampleExplicitLod_arg.cl
LLVM_SPIRV :: transcoding/float16.ll
LLVM_SPIRV :: transcoding/spec_const.ll
LLVM_SPIRV :: transcoding/sub_group_shuffle_relative.ll
LLVM_SPIRV :: transcoding/sub_group_clustered_reduce.ll
LLVM_SPIRV :: transcoding/sub_group_shuffle.ll
LLVM_SPIRV :: transcoding/image_signedness_spv_ir.ll
LLVM_SPIRV :: transcoding/sub_group_non_uniform_arithmetic.ll

[MrSidims]

I leave review to @aobolensk as he is touching code somewhere around with #174