Revert "Try again: in unix like system, set foreground process while running external command (#6273)" (#6542)

This reverts commit 1d18f6947e.

src/main.rs

@@ -135,14 +135,6 @@ fn main() -> Result<()> {
 
     let parsed_nu_cli_args = parse_commandline_args(&nushell_commandline_args, &mut engine_state);
 
-    #[cfg(target_family = "unix")]
-    {
-        // This will block SIGTSTP, SIGTTOU, SIGTTIN, and SIGCHLD, which is required
-        // for this shell to manage its own process group / children / etc.
-        nu_system::signal::block();
-        nu_system::signal::set_terminal_leader()
-    }
-
     if let Ok(ref args) = parsed_nu_cli_args {
         set_config_path(
             &mut engine_state,