SDL: Update README-migration

From 639a744ac4ef835d1e2e92834e5df640196997ed Mon Sep 17 00:00:00 2001
From: Sylvain <[EMAIL REDACTED]>
Date: Wed, 28 Dec 2022 20:22:11 +0100
Subject: [PATCH] Update README-migration

---
 docs/README-migration.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/docs/README-migration.md b/docs/README-migration.md
index 3d229d8b503e..82a2d26c8dcd 100644
--- a/docs/README-migration.md
+++ b/docs/README-migration.md
@@ -753,6 +753,8 @@ You can instead use 'SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CON
 
 SDL_VideoInit() and SDL_VideoQuit() have been removed. Instead you can call SDL_InitSubSytem() and SDL_QuitSubSytem() with SDL_INIT_VIDEO, which will properly refcount the subsystems. You can choose a specific audio driver using SDL_VIDEO_DRIVER hint.
 
+'SDL_WINDOW_SHOW' flag has been removed. It's activated by default, and can be unactivated by using SDL_WINDOW_HIDDEN
+