LibGUI: Unbreak GUI::ScrollBar default size

Oops, got my width/height mixed up here. :^)

Libraries/LibGUI/ScrollBar.cpp

@@ -100,9 +100,9 @@ ScrollBar::ScrollBar(Orientation orientation)
         s_right_arrow_bitmap = &Gfx::CharacterBitmap::create_from_ascii(s_right_arrow_bitmap_data, 9, 9).leak_ref();
 
     if (m_orientation == Orientation::Vertical) {
-        set_fixed_height(16);
-    } else {
         set_fixed_width(16);
+    } else {
+        set_fixed_height(16);
     }
 
     m_automatic_scrolling_timer->set_interval(100);