Revert fix in std win thread for unsafe_op_in_unsafe_fn

Author: bdbai

library/std/src/sys/pal/windows/thread.rs

@@ -49,7 +49,7 @@ impl Thread {
 
         unsafe extern "system" fn thread_start(main: *mut c_void) -> u32 {
             // Next, reserve some stack space for if we otherwise run out of stack.
-            unsafe { stack_overflow::reserve_stack() };
+            stack_overflow::reserve_stack();
             // Finally, let's run some code.
             // SAFETY: We are simply recreating the box that was leaked earlier.
             // It's the responsibility of the one who call `Thread::new` to ensure this is safe to call here.