docs: Added more '\threadsafety` tags.

Reference Issue #7140.

include/SDL3/SDL_audio.h

@@ -966,6 +966,8 @@ extern SDL_DECLSPEC SDL_AudioStream * SDLCALL SDL_CreateAudioStream(const SDL_Au
  * \returns a valid property ID on success or 0 on failure; call
  *          SDL_GetError() for more information.
  *
+ * \threadsafety It is safe to call this function from any thread.
+ *
  * \since This function is available since SDL 3.1.3.
  */
 extern SDL_DECLSPEC SDL_PropertiesID SDLCALL SDL_GetAudioStreamProperties(SDL_AudioStream *stream);