Update 04.lens/01.lens-main/textbook.en.md, 01.curriculum/01.physics-chemistry-biology/03.Niv3/02.Geometrical-optics/05.paraxial-optics/02.paraxial-optics-simple-elements/04.mirror/01.lens-main/textbook.en.mcd files
Deleted 01.curriculum/01.physics-chemistry-biology/03.Niv3/02.Geometrical-optics/05.paraxial-optics/02.paraxial-optics-simple-elements/04-lens/.gitkeep