Remove usage of panic_update_hook feature gate

Author: bjorn3

library/proc_macro/src/bridge/client.rs

@@ -310,15 +310,16 @@ impl Bridge<'_> {
         // NB. the server can't do this because it may use a different libstd.
         static HIDE_PANICS_DURING_EXPANSION: Once = Once::new();
         HIDE_PANICS_DURING_EXPANSION.call_once(|| {
-            panic::update_hook(move |prev, info| {
+            let prev = panic::take_hook();
+            panic::set_hook(Box::new(move |info| {
                 let show = BridgeState::with(|state| match state {
                     BridgeState::NotConnected => true,
                     BridgeState::Connected(_) | BridgeState::InUse => force_show_panics,
                 });
                 if show {
                     prev(info)
                 }
-            });
+            }));
         });
 
         BRIDGE_STATE.with(|state| state.set(BridgeState::Connected(self), f))

library/proc_macro/src/lib.rs

@@ -29,7 +29,6 @@
 #![feature(restricted_std)]
 #![feature(rustc_attrs)]
 #![feature(min_specialization)]
-#![feature(panic_update_hook)]
 #![recursion_limit = "256"]
 
 #[unstable(feature = "proc_macro_internals", issue = "27812")]