Properly implement event loop extension traits

This was implemented for `&dyn ActiveEventLoop` before, but that's less
general than implementing it directly for `dyn ActiveEventLoop`.

The `+ '_` is required to tell the compiler that we want to implement
this for all `dyn ActiveEventLoop`s, not just `'static` ones (even
though they're all going to be `'static`).

src/platform/macos.rs

@@ -396,7 +396,7 @@ pub trait ActiveEventLoopExtMacOS {
     fn allows_automatic_window_tabbing(&self) -> bool;
 }
 
-impl ActiveEventLoopExtMacOS for &dyn ActiveEventLoop {
+impl ActiveEventLoopExtMacOS for dyn ActiveEventLoop + '_ {
     fn hide_application(&self) {
         let event_loop = self
             .as_any()