fix(utime.c): make set_time correctly subtract TZONE_OFFSET

there were two bugs in set_time:

• TZONE_OFFSET is not multiplied by 1000, even though epic_rtc_set_milliseconds was used.
• TZONE_OFFSET is added in both time and set_time. set_time should subtract the timezone offset.

Testcase:

import utime

old = utime.time()
utime.set_time(old)
new = utime.time()

if old != new:
  print("time difference:", new - old)
  # will print 7607, or 2.11 hours with the old code
  # should print 0 or 1 at most

pycardium/modules/utime.c

@@ -20,7 +20,7 @@
 static mp_obj_t time_set_time(mp_obj_t secs)
 {
 	uint64_t timestamp = mp_obj_get_int(secs) * 1000ULL +
-			     EPOCH_OFFSET * 1000ULL + TZONE_OFFSET;
+			     EPOCH_OFFSET * 1000ULL - TZONE_OFFSET * 1000ULL;
 	epic_rtc_set_milliseconds(timestamp);
 	return mp_const_none;
 }