[MSX] Point overmap_horde_1 and overmap_horde_2 to overmap_horde_3 sprite (#2755)

* Create overmap_horde.json

* Update overmap_horde.json

Author: gettingusedto

gfx/MShockXotto+/pngs_overmap_32x32/overmap_horde/overmap_horde.json

@@ -0,0 +1,8 @@
+[
+  {
+    "id": [ "overmap_horde_1", "overmap_horde_2", "overmap_horde_3" ],
+    "fg": "overmap_horde_3",
+    "rotates": false,
+    "bg": [  ]
+  }
+]