fix(utime.c): Fix time zone offset handling in time_ms

Another bug in utime.c, this time in utime.time_ms():

The time zone offset is added with the wrong sign, as a result of wrong precedence when adding parentheses to the multiplication with 1000:

Testcase:

import utime

s = utime.time()
ms = utime.time_ms()
diff = s - ms // 1000

if diff != 0:
  print("time difference:", diff)
  # will print 14400, or 4 hours, with the old code
  # should print 0

pycardium/modules/utime.c

@@ -45,8 +45,8 @@ MP_DEFINE_CONST_FUN_OBJ_0(time_time_obj, time_time);
 static mp_obj_t time_time_ms(void)
 {
 	uint64_t milliseconds;
-	milliseconds = epic_rtc_get_milliseconds() -
-		       (EPOCH_OFFSET + TZONE_OFFSET) * 1000ULL;
+	milliseconds = epic_rtc_get_milliseconds() - EPOCH_OFFSET * 1000ULL +
+		       TZONE_OFFSET * 1000ULL;
 	return mp_obj_new_int_from_ull(milliseconds);
 }
 MP_DEFINE_CONST_FUN_OBJ_0(time_time_ms_obj, time_time_ms);