Fix: Command Injection Vulnerability in cleanup_cache

[Mirza-Samad-Ahmed-Baig]

This pull request resolves a critical command injection vulnerability found in the cleanup_cache function of deepcode.py. The function's use of os.system with user-controllable directory contents posed a significant security risk.

The fix replaces the vulnerable os.system calls with safer alternatives: shutil.rmtree and os.walk. These functions handle file and directory deletion securely, without invoking a shell, thereby eliminating the command injection vulnerability.

This change fortifies the application against potential attacks that could lead to arbitrary command execution and server compromise. It is a crucial security update that should be merged to protect the integrity of the application and its host environment.