docs: Note that you don't need to free SDL_GetDefaultCursor's results.

Reference Issue #6777.

(cherry picked from commit 16f8dfcef944019ce4474061aa06c2a1997e601e)

include/SDL_mouse.h

@@ -389,6 +389,9 @@ extern DECLSPEC SDL_Cursor *SDLCALL SDL_GetCursor(void);
 /**
  * Get the default cursor.
  *
+ * You do not have to call SDL_FreeCursor() on the return value,
+ * but it is safe to do so.
+ *
  * \returns the default cursor on success or NULL on failure.
  *
  * \since This function is available since SDL 2.0.0.