fix oldest samples not being removed

draw/src/container.rs

@@ -12,10 +12,11 @@ impl Container {
     }
 
     pub fn push(&mut self, data: Vec<f32>) {
+        self.data.push(data);
+
         if self.data.len() as u32 > self.max_samples {
-            self.data.pop();
+            self.data.remove(0);
         }
-        self.data.push(data)
     }
 
     pub fn iter(&self) -> std::slice::Iter<'_, Vec<f32>> {