[libc] Remove leftover target dependent intrinsic

Summary:
I forgot to remove these because I thought I did it already. This caused
the build to fail when actually linked.

Author: jhuber6

libc/src/__support/GPU/nvptx/utils.h

@@ -110,21 +110,13 @@ LIBC_INLINE uint32_t get_lane_size() { return 32; }
                                                            uint32_t x) {
   uint32_t mask = static_cast<uint32_t>(lane_mask);
   uint32_t id = __builtin_ffs(mask) - 1;
-#if __CUDA_ARCH__ >= 600
   return __nvvm_shfl_sync_idx_i32(mask, x, id, get_lane_size() - 1);
-#else
-  return __nvvm_shfl_idx_i32(x, id, get_lane_size() - 1);
-#endif
 }
 
 /// Returns a bitmask of threads in the current lane for which \p x is true.
 [[clang::convergent]] LIBC_INLINE uint64_t ballot(uint64_t lane_mask, bool x) {
   uint32_t mask = static_cast<uint32_t>(lane_mask);
-#if __CUDA_ARCH__ >= 600
   return __nvvm_vote_ballot_sync(mask, x);
-#else
-  return mask & __nvvm_vote_ballot(x);
-#endif
 }
 /// Waits for all the threads in the block to converge and issues a fence.
 [[clang::convergent]] LIBC_INLINE void sync_threads() { __syncthreads(); }