examples: Remove extern crate from composite_template example
These are not needed after the move to Rust 2018 edition.
//!
//! This sample demonstrates how to create a widget using GTK's composite templates.
-#[macro_use]
-extern crate glib;
-#[macro_use]
-extern crate gtk;
-
use gio::{prelude::ApplicationExtManual, ApplicationExt};
use glib::subclass::prelude::*;
-use glib::{Cast, StaticType};
-use gtk::WidgetExt;
+use glib::{glib_object_subclass, glib_wrapper, Cast, StaticType};
+use gtk::{CompositeTemplate, WidgetExt};
mod imp {
use super::*;
