remove unnecessary Window.Shader method

picture.go

@@ -45,8 +45,6 @@ func NewPicture(img image.Image, smooth bool) *Picture {
 }
 
 // Texture returns a pointer to the underlying OpenGL texture of a picture.
-//
-// Note, that the parent of this texture is pixelgl.NoOpDoer.
 func (p *Picture) Texture() *pixelgl.Texture {
 	return p.texture
 }

window.go

@@ -197,11 +197,6 @@ func (w *Window) Update() {
 	})
 }
 
-// Shader returns the default shader used by a window.
-func (w *Window) Shader() *pixelgl.Shader {
-	return w.shader
-}
-
 // SetClosed sets the closed flag of a window.
 //
 // This is usefull when overriding the user's attempt to close a window, or just to close a