librustdoc: render: use render_into instead of creating a temp string

Signed-off-by: Muhammad Falak R Wani <[email protected]>

Author: mfrw

src/librustdoc/html/render/print_item.rs

@@ -139,8 +139,7 @@ pub(super) fn print_item(cx: &Context<'_>, item: &clean::Item, buf: &mut Buffer,
         src_href: src_href.as_deref(),
     };
 
-    let heading = item_vars.render().unwrap();
-    buf.write_str(&heading);
+    item_vars.render_into(buf).unwrap();
 
     match *item.kind {
         clean::ModuleItem(ref m) => item_module(buf, cx, item, &m.items),