fix: src\gc.c(1425): warning C4244: '=': conversion from 'mrb_int' to 'int', possible loss of data

src/gc.c

@@ -1422,7 +1422,7 @@ gc_step_ratio_set(mrb_state *mrb, mrb_value obj)
   mrb_int ratio;
 
   mrb_get_args(mrb, "i", &ratio);
-  mrb->gc.step_ratio = ratio;
+  mrb->gc.step_ratio = (int)ratio;
   return mrb_nil_value();
 }