sdl2-compat: avoid a const warning from old compilers

SDL Commits
1 
From 4f6a3c4a02632c3414f3a2266d32a4c202d412b2 Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Tue, 8 Aug 2023 23:56:10 +0300
Subject: [PATCH] avoid a const warning from old compilers

---
 src/sdl2_compat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/sdl2_compat.c b/src/sdl2_compat.c
index 414bae1..5f5903b 100644
--- a/src/sdl2_compat.c
+++ b/src/sdl2_compat.c
@@ -4522,7 +4522,7 @@ SDL_GetNumDisplayModes(int displayIndex)
     const SDL_DisplayMode **list;
     list = SDL3_GetFullscreenDisplayModes(displayID, &count);
     if (list) {
-        SDL3_free(list);
+        SDL3_free((void*)list);
         return count;
     }
     return -1;