fix syntax

docs/how-to/draw-boxes-around-subfigures.md

@@ -4,7 +4,7 @@ If you want to show that several elements in a `Figure` belong together, you can
 The trick is to use a nested `GridLayout` for each group of objects and place a `Box` at the same position as this `GridLayout`.
 Then the `alignmode = Outside(some_padding)` ensures that objects with protrusions sticking out, like `Axis`, are fully contained within the enclosing boxes.
 
-\begin{examplefigure}
+\begin{examplefigure}{}
 ```julia
 using CairoMakie
 CairoMakie.activate!() # hide