Allow float dtype when Autocast CPU Disabled (#107348)
**Summary**
Fix the https://github.com/pytorch/pytorch/issues/100565 by allowing float32 data type when Autocast CPU is disabled. Current behavior is:
- When autocast is disabled and user passes in float data type, it works well.
- When autocast is enabled and user passes in float data type, a warn message throws `UserWarning: In CPU autocast, but the target dtype is not supported. Disabling autocast.` to disable autocast automatically
**TestPlan**
```
python -u -m pytest -s -v test_autocast.py -k test_autocast_disabled_with_fp32_dtype
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/107348
Approved by: https://github.com/jgong5, https://github.com/Neilblaze, https://github.com/albanD
