Add back Box use

Author: vbfox

src/font/system.rs

@@ -1,5 +1,6 @@
 use crate::{Attrs, Font, FontMatchAttrs, HashMap, ShapeBuffer};
 use alloc::collections::BTreeSet;
+use alloc::boxed::Box;
 use alloc::string::String;
 use alloc::sync::Arc;
 use alloc::vec::Vec;