Fork choice: Remove redundant check in validate_on_attestation

[paulhauner]

Removes a redundant check from fork choice validate_on_attestation.

assert target.epoch in [current_epoch, previous_epoch] already asserts this.

I've raised this for a few reasons:

• To ensure I'm not missing something.
• If it's impossible to hit then it's impossible to test and I think we should remove it.
• The "... delay consideration ..." note becomes ineffective if we can never reach it.

[djrtwo]

You are correct, but I might argue for still having the a comment above assert target.epoch in [current_epoch, previous_epoch] that says # If attestation target is from a future epoch, delay consideration until the epoch arrives

[paulhauner]

You are correct, but I might argue for still having the a comment above assert target.epoch in [current_epoch, previous_epoch] that says # If attestation target is from a future epoch, delay consideration until the epoch arrives

Done :)

[djrtwo]

Thanks!

Will release in v0.11.3 or v0.12 whichever comes next