eval.c: Free the stack with FREE_LIST instead of FREE_OBJ

This way we pass the correct oldsize to the allocator.

src/eval.c

@@ -349,7 +349,7 @@ apfl_ctx_destroy(apfl_ctx ctx)
     while (ctx->stack_len > 0) {
         stack_must_drop(ctx, -1);
     }
-    FREE_OBJ(ctx->allocator, ctx->stack);
+    FREE_LIST(ctx->allocator, ctx->stack, ctx->stack_cap);
     FREE_OBJ(ctx->allocator, ctx);
 }