SDL_image: Bump libwebp (d7616)

SDL Commits
#1 
From d761600d480e7ffa1ac579e1447da7aede732d3e Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Thu, 2 Mar 2023 10:15:50 +0300
Subject: [PATCH] Bump libwebp

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

diff --git a/external/libwebp b/external/libwebp
index 12cf7b31..918d4284 160000
--- a/external/libwebp
+++ b/external/libwebp
@@ -1 +1 @@
-Subproject commit 12cf7b315fb7a9df56fa6b8ee30e36312659d63c
+Subproject commit 918d428493e2dcc32e0d680816515637eb66ce7e