Remove extra tick

[hwwhww]

Thank @rolfyone for reporting it!

https://media.githubusercontent.com/media/ethereum/consensus-spec-tests/master/tests/mainnet/bellatrix/fork_choice/should_override_forkchoice_update/pyspec_tests/should_override_forkchoice_update__true/steps.yaml

There is a tick 1573 after tick 1576, which should be impossible.

Another further bug-free fix is to add the precondition assert time > store.time in on_tick function, given that we have stated " on_tick(store, time) whenever time > store.time where time is the current Unix time". I'll open another PR for it.

[rolfyone]

LGTM, I think theres a similar incident in capella

- {block: block_0x129d58f5945e490563ba0da2bdf1b3df1ce7577901b37c542d8e27ea349046f9,
  valid: true}
- checks:
    time: 212
    head: {slot: 35, root: '0xa540106e6971b4322e43ca5975de038c2a42351ec589be7f29eeaa6dd8cf7ff5'}
    justified_checkpoint: {epoch: 3, root: '0x7385661d892adb7018c4440b8c3ffeb743303643ddb718aa14e4193c32d96df5'}
    finalized_checkpoint: {epoch: 2, root: '0xc2899f74e6ea5681dd3658cc50ff405fe7077494eea3b97404fe2781934c2082'}
    proposer_boost_root: '0x0000000000000000000000000000000000000000000000000000000000000000'
- {tick: 211}
- checks:
    time: 211
    head: {slot: 35, root: '0xa540106e6971b4322e43ca5975de038c2a42351ec589be7f29eeaa6dd8cf7ff5'}
    justified_checkpoint: {epoch: 3, root: '0x7385661d892adb7018c4440b8c3ffeb743303643ddb718aa14e4193c32d96df5'}
    finalized_checkpoint: {epoch: 2, root: '0xc2899f74e6ea5681dd3658cc50ff405fe7077494eea3b97404fe2781934c2082'}
    proposer_boost_root: '0x0000000000000000000000000000000000000000000000000000000000000000'
    

If I understand correctly, these should be cleaned up by this change too :)