Fix clippy: use &mut str instead of &mut String in unused param

Fixes ptr_arg lint on Rust 1.88 clippy for TemplatesButton::show_submenu.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: userFRM

src/ui/drawing_toolbar/utilities/templates.rs

@@ -36,7 +36,7 @@ impl TemplatesButton {
         sidebar_rect: Rect,
         category_rect: Option<Rect>,
         templates: &[DrawingTemplate],
-        _template_name_input: &mut String,
+        _template_name_input: &mut str,
         _show_name_input: bool,
     ) -> Option<DrawingToolbarAction> {
         let mut builder = SubmenuBuilder::new(ui, sidebar_rect)