Delete validator account

[JustinDrake]

I accidentally added an incorrect validator account using lighthouse account validator import. I can't see a subcommand to delete it.

SUBCOMMANDS:
    create                 Creates new validators from an existing EIP-2386 wallet using the EIP-2333 HD key
                           derivation scheme.
    exit                   Submits a VoluntaryExit to the beacon chain for a given validator keystore.
    help                   Prints this message or the help of the given subcommand(s)
    import                 Imports one or more EIP-2335 passwords into a Lighthouse VC directory, requesting
                           passwords interactively. The directory flag provides a convenient method for importing a
                           directory of keys generated by the eth2-deposit-cli Python utility.
    list                   Lists the public keys of all validators.
    recover                Recovers validator private keys given a BIP-39 mnemonic phrase. If you did not specify a
                           `--first-index` or count `--count`, by default this will only recover the keys associated
                           with the validator at index 0 for an HD wallet in accordance with the EIP-2333 spec.
    slashing-protection    Import or export slashing protection data to or from another client

[AgeManning]

There isn't one (yet). You should be able to remove it from the directory default is ~/.lighthouse/mainnet/validators.

If you have already run the validator client you may need to remove it from the validator_definitions.yml in the same directory.

[louqash]

I'll get onto that!

[michaelsproul]

Full deletion is now available via the keymanager API: https://ethereum.github.io/keymanager-APIs/#/Local%20Key%20Manager/deleteKeys

A CLI interface for the API is being developed in https://github.com/sigp/lighthouse/pull/3502