simulator: Fix Failed to initialize dependency logging (#7393)

The simulator works but always emits the following message:

```
$ cargo run --release --bin simulator basic-sim
...
...
Failed to initialize dependency logging: attempted to set a logger after the logging system was already initialized
...
...
```


  This PR removes the initialization with `env_logger`.

(Update)
With https://github.com/sigp/lighthouse/pull/7433 merged, the libp2p/discv5 logs are saved in separate files and respect the `RUST_LOG` env var for log level configuration.

Cargo.lock

@@ -8469,9 +8469,7 @@ name = "simulator"
 version = "0.2.0"
 dependencies = [
  "clap",
- "env_logger 0.9.3",
  "environment",
- "eth2_network_config",
  "execution_layer",
  "futures",
  "kzg",

testing/simulator/Cargo.toml

@@ -7,9 +7,7 @@ edition = { workspace = true }
 
 [dependencies]
 clap = { workspace = true }
-env_logger = { workspace = true }
 environment = { workspace = true }
-eth2_network_config = { workspace = true }
 execution_layer = { workspace = true }
 futures = { workspace = true }
 kzg = { workspace = true }

testing/simulator/src/main.rs

@@ -18,16 +18,12 @@ mod local_network;
 mod retry;
 
 use cli::cli_app;
-use env_logger::{Builder, Env};
 use local_network::LocalNetwork;
 use types::MinimalEthSpec;
 
 pub type E = MinimalEthSpec;
 
 fn main() {
-    // Debugging output for libp2p and external crates.
-    Builder::from_env(Env::default()).init();
-
     let matches = cli_app().get_matches();
     match matches.subcommand_name() {
         Some("basic-sim") => match basic_sim::run_basic_sim(&matches) {