SDL: include: Fixed a C++-style single line comment.

SDL Commits
1 
From 78725dc0cd8502a91d2565af44ff9e6e65f0f30d Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Sat, 17 Dec 2022 23:52:04 -0500
Subject: [PATCH] include: Fixed a C++-style single line comment.

Reference Issue #6838.
---
 include/SDL3/SDL_mutex.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/SDL3/SDL_mutex.h b/include/SDL3/SDL_mutex.h
index a3b2bc35b348..44109c383c96 100644
--- a/include/SDL3/SDL_mutex.h
+++ b/include/SDL3/SDL_mutex.h
@@ -39,7 +39,7 @@
     defined(__clang__) && (!defined(SWIG))
 #define SDL_THREAD_ANNOTATION_ATTRIBUTE__(x)   __attribute__((x))
 #else
-#define SDL_THREAD_ANNOTATION_ATTRIBUTE__(x)   // no-op
+#define SDL_THREAD_ANNOTATION_ATTRIBUTE__(x)   /* no-op */
 #endif
 
 #define SDL_CAPABILITY(x) \