cleanup: remove misleading (void)reasonType — variable IS used below

The cast falsely suggests reasonType is unused, but it's read on lines
3699-3702 for AFK/vote-kick differentiation. Same class of issue as
the (void)isPlayerTarget fix in commit 6731e584.

src/game/game_handler.cpp

@@ -3691,8 +3691,7 @@ void GameHandler::registerOpcodeHandlers() {
         std::string reason;
         if (packet.hasData())
             reason = packet.readString();
-        (void)kickerGuid;
-        (void)reasonType;
+        (void)kickerGuid;  // not displayed; reasonType IS used below
         std::string msg = "You have been removed from the group.";
         if (!reason.empty())
             msg = "You have been removed from the group: " + reason;