Remove dead code (unused as of d5391686a) (#1022)

src/platform_impl/macos/util/into_option.rs

@@ -1,14 +0,0 @@
-use cocoa::base::{id, nil};
-
-pub trait IntoOption: Sized {
-    fn into_option(self) -> Option<Self>;
-}
-
-impl IntoOption for id {
-    fn into_option(self) -> Option<Self> {
-        match self != nil {
-            true => Some(self),
-            false => None,
-        }
-    }
-}