Eliminate dead code before torch version 2.4

[bowenyang008]

What does this PR do?

Remove dead code which is only effective before torch 2.4, which we don't support anymore.

What issue(s) does this change relate to?

1. Pave the way to support and release torch 2.7 and deprecate torch 2.4/2.5
2. Test Cursor on trivial SDE task

Changes by AI coder

Most changes are created by Cursor, yet reviewed by myself. Workflow:
Codebase wise one shot change is still hard for Cursor, so current flow is:

1. Use agent mode in Cursor
2. Use Claude 3.7 non-thinking
3. 
For file in target_files:
    prompt("currently we support torch versions between 2.4 and 2.6, can you help me apply necessary changes to remove or clean up code related to torch version less than 2.4 in this @file? Please don't modify other comments or docstrings. When you need to delete a function please consider if it is used by other files in @composer as well.")