SDL: docs: fix window flags in README-migration.md

SDL Commits
1 
From f9bffa31b6f1234fed431d7dacec9c825ff44478 Mon Sep 17 00:00:00 2001
From: anton-kl <[EMAIL REDACTED]>
Date: Tue, 22 Oct 2024 07:35:08 +0100
Subject: [PATCH] docs: fix window flags in README-migration.md

Use correct SDL macro instead of invalid "flags" string.
Also add a comment about preferred approach.
---
 docs/README-migration.md | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/docs/README-migration.md b/docs/README-migration.md
index 0d451453221f0..0715181abcc48 100644
--- a/docs/README-migration.md
+++ b/docs/README-migration.md
@@ -2134,7 +2134,9 @@ SDL_CreateWindow() has been simplified and no longer takes a window position. Yo
     SDL_SetNumberProperty(props, SDL_PROP_WINDOW_CREATE_Y_NUMBER, y);
     SDL_SetNumberProperty(props, SDL_PROP_WINDOW_CREATE_WIDTH_NUMBER, width);
     SDL_SetNumberProperty(props, SDL_PROP_WINDOW_CREATE_HEIGHT_NUMBER, height);
-    SDL_SetNumberProperty(props, "flags", flags);
+    // For window flags you should use separate window creation properties,
+    // but for easier migration from SDL2 you can use the following:
+    SDL_SetNumberProperty(props, SDL_PROP_WINDOW_CREATE_FLAGS_NUMBER, flags);
     pWindow = SDL_CreateWindowWithProperties(props);
     SDL_DestroyProperties(props);
     if (window) {