Prevent propagation of voided vertices in `on_new_tx()`

[glevco]

          @msbrogli commented on https://github.com/HathorNetwork/hathor-core-side-dag/pull/11#discussion_r1634980005:

Nice rule. I guess we can add it to the on_new_tx() propagation part.

Originally posted by @glevco in #1061 (comment)

[jansegre]

Is this specific to sync-v2? Either way we'd need a careful examination before doing this.

[glevco]

I don't think this is too relevant for now, specially since I'm refactoring multiple parts of the P2P and specifically this PR changes this. Maybe we can leave it on hold and review it again in the future.