Skin: Remove extra "Submenu_opacity"

Author: bonzibudd

Src/Skins/Metro/SkinDescription.txt

@@ -105,7 +105,6 @@ Submenu_padding=2,2,2,2
 
 ; These have the same meaning as the Main_... properties
 Submenu_opacity=region
-Submenu_opacity=region
 Submenu_bitmap=$SystemAccentDark1|$StartBackground
 Submenu_bitmap_tint1=$StartHighlight
 Submenu_bitmap_mask=2