rwlock: SDL_UnlockRWLock was incorrectly tagged with SDL_RELEASE_SHARED.

It needs to be SDL_RELEASE_GENERIC, because it releases both exclusive
(writer) and shared (reader) locks.

Without this fix, clang's `-Wthread-safety` tests generate incorrect warnings.

Reference Issue #8096.

include/SDL3/SDL_mutex.h

@@ -433,7 +433,7 @@ extern DECLSPEC int SDLCALL SDL_TryLockRWLockForWriting(SDL_RWLock *rwlock) SDL_
  *
  * \since This function is available since SDL 3.0.0.
  */
-extern DECLSPEC int SDLCALL SDL_UnlockRWLock(SDL_RWLock *rwlock) SDL_RELEASE_SHARED(rwlock);
+extern DECLSPEC int SDLCALL SDL_UnlockRWLock(SDL_RWLock *rwlock) SDL_RELEASE_GENERIC(rwlock);
 
 /**
  * Destroy a read/write lock created with SDL_CreateRWLock().