Backends: SDL3: Fix leak of SDL_GetGamepads() return value (#7381)

backends/imgui_impl_sdl3.cpp

@@ -609,6 +609,7 @@ static void ImGui_ImplSDL3_UpdateGamepads()
                 if (bd->GamepadMode == ImGui_ImplSDL3_GamepadMode_AutoFirst)
                     break;
             }
+        SDL_free(sdl_gamepads);
         bd->WantUpdateGamepadsList = false;
     }