Flaky test: nakamoto_integrations::flash_blocks_on_epoch_3

[jbencin]

This test is flaky and sometimes fails

Example in CI: https://github.com/stacks-network/stacks-core/actions/runs/12960831292/job/36155549996?pr=5746#step:6:2253

The error:

thread 'tests::nakamoto_integrations::flash_blocks_on_epoch_3' panicked at testnet/stacks-node/src/tests/nakamoto_integrations.rs:1837:5:
assertion `left == right` failed: Burn chain tip should have advanced by 4 blocks
  left: 231
 right: 233

It looks like we need to give it some time to process the new burn blocks, but if I add a sleep() I get other failures later

Do we actually need this test? It looks like it's testing Epoch 2 -> 3 transition, which has already happened and doesn't need further testing

[obycode]

Yeah, that feels like it could be ignored now if it's troublesome, similar to what we did with the test for disabling microblocks at 2.5.