Rename song constants using Japanese sound test menu

data/maps/PewterCity_Gym/map.json

@@ -2,7 +2,7 @@
   "id": "MAP_PEWTER_CITY_GYM",
   "name": "PewterCity_Gym",
   "layout": "LAYOUT_PEWTER_CITY_GYM",
-  "music": "BGM_FRLG_GYM",
+  "music": "MUS_GYM",
   "region_map_section": "MAPSEC_PEWTER_CITY",
   "requires_flash": false,
   "weather": "WEATHER_NONE",

data/maps/PewterCity_Gym/text.inc

@@ -12,7 +12,7 @@ Text_190CD4:: @ 8190CD4
     .string "That's the TRAINER's honor that\n"
     .string "compels you to challenge me.\p"
     .string "Fine, then!\n"
-    .string "Show me your best!{PLAY_BGM}{BGM_FRLG_LEADER_EYE}$"
+    .string "Show me your best!{PLAY_BGM}{MUS_EXEYE}$"
 
 Text_190E4F:: @ 8190E4F
     .string "I took you for granted, and so\n"