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.

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 }