bug: flaky RLN test

[gabrielmer]

Problem

A clear and concise description of what the bug is.

The test WakuNode - RLN relay::clearNullifierLog: should clear epochs > MaxEpochGap is extremely flaky in the CI and constantly get this error

  /Users/runner/work/nwaku/nwaku/build/all_tests_waku 'WakuNode - RLN relay::clearNullifierLog: should clear epochs > MaxEpochGap'
----------------------------------------------------
    /Users/runner/work/nwaku/nwaku/tests/waku_rln_relay/test_wakunode_rln_relay.nim(585, 44): Check failed: node2.wakuRlnRelay.nullifierLog.len() == 4
    node2.wakuRlnRelay.nullifierLog.len() was 3
    /Users/runner/work/nwaku/nwaku/tests/waku_rln_relay/test_wakunode_rln_relay.nim(594, 44): Check failed: node2.wakuRlnRelay.nullifierLog.len() == 4
    node2.wakuRlnRelay.nullifierLog.len() was 3

  [FAILED ] (  41.8s) clearNullifierLog: should clear epochs > MaxEpochGap

Expected behavior

The test should give consistent results

nwaku version/commit hash

1d2b910