Revise local-net script

[kstdl]

Revise local-net script. We have options for bootnodes count and we was creating this bootnodes old way by adding argument to taraxad, but we already using separate binaries. https://github.com/Taraxa-project/taraxa-node/blob/develop/for_devs/local-net#L128 Looks like we don't need bootnodes for local-net at all