vo_gpu_next: correctly clear removed hooks

Before d208284, this was implicitly reset back to 0 at the start of
every update_options(). But we no longer explicitly reset par->params,
so we need to do it manually here for the hooks.

Fixes: mpv-player#12203

video/out/vo_gpu_next.c

@@ -2034,6 +2034,7 @@ static void update_render_options(struct vo *vo)
 
     update_icc_opts(p, opts->icc_opts);
 
+    pars->params.num_hooks = 0;
     const struct pl_hook *hook;
     for (int i = 0; opts->user_shaders && opts->user_shaders[i]; i++) {
         if ((hook = load_hook(p, opts->user_shaders[i]))) {