numeric.c (mrb_float_to_integer): isinf/isnan takes any float values.

So don't need to cast to `float`, just use `mrb_float`.

src/numeric.c

@@ -1766,7 +1766,7 @@ mrb_float_to_integer(mrb_state *mrb, mrb_value x)
   if (!mrb_float_p(x)) {
     mrb_raise(mrb, E_TYPE_ERROR, "non float value");
   }
-  float f = mrb_float(x);
+  mrb_float f = mrb_float(x);
   if (isinf(f) || isnan(f)) {
     mrb_raisef(mrb, E_RANGE_ERROR, "float %f out of range", f);
   }