Guide users to install cuda with explicit lable with conda

[IvanaGyro]

In https://github.com/Cytnx-dev/Cytnx/blob/6f67dd45cbee73f73fded1baa4715ef2f8cdde74/docs/source/adv_install.rst, we guide users install cuda with the command

conda install -c nvidia cuda

This will cause version resolving problem when users want to install other package from conda-forge channel:

InvalidSpec: The package "nvidia/linux-64::cuda-compiler==12.5.0=0" is not available for the specified platform

A comment in google-deepmind/alphafold#945 (comment) suggested to install cuda with

conda install -c nvidia/label/cuda-12.6.3 cuda

to avoid the version resolving problem.

[IvanaGyro]

Using explicit label while installing cuda doesn't work. And conda/conda#14063 is the issue related to this version tracking problem on Conda.