Updated documentation to reflect that SDL_GetHint() is thread-safe

This was fixed at some point, so this updates the documentation to match.

Fixes https://github.com/libsdl-org/SDL/issues/13932

include/SDL3/SDL_hints.h

@@ -4558,12 +4558,7 @@ extern SDL_DECLSPEC void SDLCALL SDL_ResetHints(void);
  * \param name the hint to query.
  * \returns the string value of a hint or NULL if the hint isn't set.
  *
- * \threadsafety It is safe to call this function from any thread, however the
- *               return value only remains valid until the hint is changed; if
- *               another thread might do so, the app should supply locks
- *               and/or make a copy of the string. Note that using a hint
- *               callback instead is always thread-safe, as SDL holds a lock
- *               on the thread subsystem during the callback.
+ * \threadsafety It is safe to call this function from any thread.
  *
  * \since This function is available since SDL 3.2.0.
  *