Fix torch models on cpu

[cning112]

Description

To make torch-based models runnable when cuda is unavailable

Motivation and Context

Some of the benchmark examples (such as GATs) doesn't run when cpu-only because of the missing map_location argument in torch.load() function

How Has This Been Tested?

• Pass the test by running: pytest qlib/tests/test_all_pipeline.py under upper directory of qlib.
• If you are adding a new feature, test on your own test scripts.

Screenshots of Test Results (if appropriate):

1. Pipeline test:
2. Your own tests:

Types of changes

• Fix bugs
• Add new feature
• Update documentation

[you-n-g]

Thanks! It looks great!