Revert "fix: set TERM env variable for terminal to fix Delete key not working…" (#13894)

This reverts commit bba57069a8.

src/server/terminal_service.rs

@@ -774,11 +774,6 @@ impl TerminalServiceProxy {
         #[allow(unused_mut)]
         let mut cmd = CommandBuilder::new(&shell);
 
-        // Set TERM environment variable to ensure proper handling of control sequences
-        // This fixes issues with Delete/Backspace keys not working correctly
-        // See: https://github.com/rustdesk/rustdesk/issues/13621
-        cmd.env("TERM", "xterm-256color");
-
         #[cfg(target_os = "windows")]
         if let Some(token) = &self.user_token {
             cmd.set_user_token(*token as _);