Fix beacon-processor-max-workers (#4636)

## Issue Addressed

Fixes a bug in the handling of `--beacon-process-max-workers` which caused it to have no effect.

## Proposed Changes

For this PR I channeled @ethDreamer and saw deep into the faulty CLI config -- this bug is almost identical to the one Mark found and fixed in #4622.

beacon_node/client/src/builder.rs

@@ -29,7 +29,6 @@ use network::{NetworkConfig, NetworkSenders, NetworkService};
 use slasher::Slasher;
 use slasher_service::SlasherService;
 use slog::{debug, info, warn, Logger};
-use std::cmp;
 use std::net::TcpListener;
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
@@ -757,7 +756,6 @@ where
                 BeaconProcessor {
                     network_globals: network_globals.clone(),
                     executor: beacon_processor_context.executor.clone(),
-                    max_workers: cmp::max(1, num_cpus::get()),
                     current_workers: 0,
                     config: beacon_processor_config,
                     log: beacon_processor_context.log().clone(),