Update cheatsheet.en.md

01.curriculum/01.physics-chemistry-biology/02.Niv2/04.optics/04.use-of-basic-optical-elements/02.mirror/02.new-course-overview/cheatsheet.en.md

@@ -148,8 +148,6 @@ side* of the mirror.<br><br>
 
 [Click here for geogebra animation](https://www.geogebra.org/m/jwgy9q7z)
 
-[Click here for geogebra animation](https://www.geogebra.org/material/iframe/id/zqwazusz)
-
 * with **real objects** 
 
 ![](Thin-spherical-mirror-InfAC-1000.jpg)<br>