No longer put condvars on the 'unsupported' platform in a box.

These condvars are unsupported and implemented as a ZST, so can be moved
without problems.

Author: m-ou-se

library/std/src/sys/unsupported/condvar.rs

@@ -3,7 +3,7 @@ use crate::time::Duration;
 
 pub struct Condvar {}
 
-pub type MovableCondvar = Box<Condvar>;
+pub type MovableCondvar = Condvar;
 
 impl Condvar {
     pub const fn new() -> Condvar {