Update lime.py

[yuzhaouoe]

Convert tensor's dtype to "float" before moving to CPU, which avoids errors when using "bf16"

Description

add .float() before .cpu() to support half precision data type

Checklist

• [ ] I've read the CODE_OF_CONDUCT.md document.
• [ ] I've read the CONTRIBUTING.md guide.
• [ ] I've successfully run the style checks using make fix-style.
• [ ] I've written tests for all new methods and classes that I created and successfully ran make test.
• [ ] I've written the docstring in Google format for all the methods and classes that I used.