Use explicit epaint over paint alias (re-export)

egui reexports the `epaint` crate both under its original name
and under the alias `paint` (for historical reasons)

egui_demo_lib/src/apps/demo/dancing_strings.rs

@@ -54,7 +54,7 @@ impl super::View for DancingStrings {
                     .collect();
 
                 let thickness = 10.0 / mode;
-                shapes.push(paint::Shape::line(
+                shapes.push(epaint::Shape::line(
                     points,
                     Stroke::new(thickness, Color32::from_additive_luminance(196)),
                 ));