SDL_mixer: bump libgme to update gme.h.

From cf10cbe7c9643f94ad239da2805058c53aa75d11 Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Thu, 21 Sep 2023 14:32:10 +0200
Subject: [PATCH] bump libgme to update gme.h.

---
 external/libgme | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/external/libgme b/external/libgme
index 56a7f868..9cca58bc 160000
--- a/external/libgme
+++ b/external/libgme
@@ -1 +1 @@
-Subproject commit 56a7f868b85d874a07be4b68cc97992a13089bd6
+Subproject commit 9cca58bcb1c2f6891042223f05d7bf60f82b4afb