SDL_image: upgrade vendored libpng to 1.6.48 (5b681)

From 5b681f0b418363c6be08857f62ae8d03cc5e84c1 Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Tue, 13 May 2025 23:10:04 +0300
Subject: [PATCH] upgrade vendored libpng to 1.6.48

---
 .gitmodules     | 2 +-
 external/libpng | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/.gitmodules b/.gitmodules
index a195f8e7..2cd1f114 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -5,7 +5,7 @@
 [submodule "external/libpng"]
 	path = external/libpng
 	url = https://github.com/libsdl-org/libpng.git
-	branch = v1.6.47-SDL
+	branch = v1.6.48-SDL
 [submodule "external/libwebp"]
 	path = external/libwebp
 	url = https://github.com/libsdl-org/libwebp.git
diff --git a/external/libpng b/external/libpng
index d5f3b730..25d73b56 160000
--- a/external/libpng
+++ b/external/libpng
@@ -1 +1 @@
-Subproject commit d5f3b730390cbbf9f1086a4aa97b7d44e42919ae
+Subproject commit 25d73b565d9903eaeb62ebebccf9d0533205e416