Fix code distance C++ unit tests for ROCm on MI250

# Summary

TestGpuIndexIVFPQ.Query_L2_MMCodeDistance
TestGpuIndexIVFPQ.Query_IP_MMCodeDistance

# Platform

ROCm

Running on:
- [x] CPU
- [ ] GPU

Interface: 
- [x] C++
- [ ] Python

# Reproduction instructions

GitHub CI