SDL: Sync SDL3 wiki -> header (195c5)

From 195c518d78138a9f6ed910cbc873d52848978a27 Mon Sep 17 00:00:00 2001
From: SDL Wiki Bot <[EMAIL REDACTED]>
Date: Mon, 13 Oct 2025 06:04:12 +0000
Subject: [PATCH] Sync SDL3 wiki -> header

[ci skip]
---
 include/SDL3/SDL_thread.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/SDL3/SDL_thread.h b/include/SDL3/SDL_thread.h
index e981b54293210..bde1bbcd72532 100644
--- a/include/SDL3/SDL_thread.h
+++ b/include/SDL3/SDL_thread.h
@@ -37,7 +37,8 @@
  * will report failure without doing anything.
  *
  * If you're going to work with threads, you almost certainly need to have a
- * good understanding of [CategoryMutex](CategoryMutex) as well.
+ * good understanding of thread safety measures: locking and synchronization
+ * mechanisms are handled by the functions in SDL_mutex.h.
  */
 
 #include <SDL3/SDL_stdinc.h>