Remove eth1 deposit functionality (#1780)

## Issue Addressed

- Resolves #1727

## Proposed Changes

Remove the `lighthouse account validator deposit` command.

It's a shame to let this go, but it's currently lacking any tests and contains significant, un-handled edge-cases (e.g., it will wait forever until the eth1 node gives a tx confirmation and if you ctrl+c it before it finishes it will leave the filesystem in an unknown state with lockfiles lying around)

I don't think we need to make deposit functionality a priority before mainnet, we have bigger fish to fry IMO.

We, will need to revive this functionality before the next testnet, but I think we should make private, non-production tools to handle this for SigP internally.

## Additional Info

Be sure to re-open #1331 if this PR is abandoned.

account_manager/Cargo.toml

@@ -11,7 +11,6 @@ slog = "2.5.2"
 slog-term = "2.6.0"
 slog-async = "2.5.0"
 types = { path = "../consensus/types" }
-state_processing = { path = "../consensus/state_processing" }
 dirs = "3.0.1"
 environment = { path = "../lighthouse/environment" }
 deposit_contract = { path = "../common/deposit_contract" }
@@ -21,7 +20,6 @@ eth2_ssz_derive = "0.1.0"
 hex = "0.4.2"
 rayon = "1.4.1"
 eth2_testnet_config = { path = "../common/eth2_testnet_config" }
-web3 = "0.11.0"
 futures = { version = "0.3.5", features = ["compat"] }
 clap_utils = { path = "../common/clap_utils" }
 directory = { path = "../common/directory" }