Run only Amsterdam for pypy3 CI until we resolve memory issues #2055
Description
#2029 describes our current issues. We weren't able to find a good configuration of memory / GC for pypy3 CI runs where we could add --until=Amsterdam and it wouldn't run out of memory. We can maybe lower the number of runners but this would take a very long time to run on each PR. For now, we agreed to only run Amsterdam (--fork=Amsterdam) for these pypy3 runs, so we should add this change for now.