remove context from ui (again) and create weird trait for it

src/testing/render/mod.rs

@@ -21,7 +21,7 @@ pub struct Renderer {
 }
 
 impl Renderer {
-    pub fn update<Ctx>(&mut self, updates: &mut Ui<Ctx>) {
+    pub fn update(&mut self, updates: &mut Ui) {
         self.ui.update(&self.device, &self.queue, updates);
     }