Sdl_mixer doesn't automatically free channels

In this version when I use SDL_mixer (1, not 2) at the end of the playing the channel is not freed as before.
I switched to the SDL2 version and it works.

**Version of emscripten/emsdk:**
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.47 (431685f05c67f0424c11473cc16798b9587bb536)
clang version 18.0.0 (https://github.com/llvm/llvm-project 21030b9ab4487d845e29792063f5666d8c4b8e09)
Target: wasm32-unknown-emscripten
Thread model: posix