Fix the old-man demo bag to show 1 Poke Ball in Yellow, 50 in Red/Blue

Confirmed against pokeyellow's engine/battle/core.asm: the Viridian
old man's demo and Oak's Pikachu catch share the same canned
one-item bag (SimulatedInputBattleItemList), quantity 1 -- pokered's
equivalent (OldManItemList, old man only, no Pikachu battle type) is
quantity 50. The port hardcoded x50 for both versions.

src/battle/BattleState.lua

@@ -2194,8 +2194,14 @@ function BattleState:openOldManBag()
   self.afterQueue = "menu"
   self:ui(function()
     local list
+    -- The canned one-item bag (POKE_BALL, neither reading from the real
+    -- inventory) differs by version: pokered's OldManItemList (core.asm
+    -- :2212-2214) is quantity 50; pokeyellow's SimulatedInputBattleItemList
+    -- (core.asm:2316-2319), shared by both the Viridian old man's demo and
+    -- Oak's Pikachu catch, dropped that to quantity 1.
+    local qty = require("src.core.GameVersion").isYellow() and "x1" or "x50"
     list = ListMenu.new(game, "ITEMS", {
-      { value = "POKE_BALL", label = Strings("POKé BALL"), right = "x50" },
+      { value = "POKE_BALL", label = Strings("POKé BALL"), right = qty },
     }, {
       script = function(l)
         l.scriptTimer = (l.scriptTimer or 0) + 1