Remove unused function

Author: bjorn3

library/std/src/sys_common/thread_info.rs

@@ -42,7 +42,3 @@ pub fn set(stack_guard: Option<Guard>, thread: Thread) {
     THREAD_INFO.with(|c| assert!(c.borrow().is_none()));
     THREAD_INFO.with(move |c| *c.borrow_mut() = Some(ThreadInfo { stack_guard, thread }));
 }
-
-pub fn reset_guard(stack_guard: Option<Guard>) {
-    THREAD_INFO.with(move |c| c.borrow_mut().as_mut().unwrap().stack_guard = stack_guard);
-}