Update sidebar GUI test

Author: GuillaumeGomez

tests/gui/sidebar.goml

@@ -18,7 +18,7 @@ define-function: (
 
         // We now hide the sidebar.
         click: "#sidebar-toggle"
-        wait-for: "body.sidebar-hidden"
+        wait-for-css: ("#sidebar", {"display": "none"})
         // `transform` is 0.3s so we need to wait a bit (0.5s) to ensure the animation is done.
         wait-for: 5000
         assert-css-false: ("#sidebar", {"transform": "none"})
@@ -37,7 +37,7 @@ define-function: (
 
         // We expand the sidebar.
         click: "#sidebar-toggle"
-        wait-for: "body.sidebar-visible"
+        wait-for-css-false: ("#sidebar", {"display": "none"})
         // `transform` is 0.3s so we need to wait a bit (0.5s) to ensure the animation is done.
         wait-for: 5000
         assert-css-false: ("#sidebar", {"transform": "matrix(1, 0, 0, 1, -308, 0)"})