Update GREF with WeaponSlot comment

optionals/compat_rhs_gref3/CfgWeapons.hpp

@@ -98,6 +98,8 @@ class CfgWeapons {
             };
         };
         class WeaponSlotsInfo: WeaponSlotsInfo {
+            // One WeaponSlot with a positive value for iconScale forces game to use icon overlay method.
+            // Required, because the inventory icon has no accessory variants.
             class MuzzleSlot {
                 iconScale = 0.1;
             };