Sketcher: Remove Snell's Law from toolbar

Leave menu item intact so it is still accessible, but does not use up toolbar space.

src/Mod/Sketcher/Gui/Workbench.cpp

@@ -344,7 +344,7 @@ inline void SketcherAddWorkbenchConstraints<Gui::ToolBarItem>(Gui::ToolBarItem&
             << "Sketcher_ConstrainDistance"
             << "Sketcher_CompConstrainRadDia"
             << "Sketcher_ConstrainAngle"
-            << "Sketcher_ConstrainSnellsLaw"
+            // << "Sketcher_ConstrainSnellsLaw" // Rarely used, show only in menu
             // << "Sketcher_ConstrainInternalAlignment" // This constrain is never used by the user - Do not use precious toolbar space
             << "Separator"
             << "Sketcher_ToggleDrivingConstraint"