refactor(examples): use tokio instead of async-std in identify example (#5579)

## Description

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Following on issue #4449 
refactor: use tokio instead of async-std in the identify example and
remove unnecesary dependencies

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## Change checklist

* Removed unnecessary dependencies on examples/identify/Cargo.toml

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- [x] I have performed a self-review of my own code
- [ ] I have made corresponding changes to the documentation
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] A changelog entry has been made in the appropriate crates

---------

Co-authored-by: David E. Perez Negron R. <[email protected]>
Co-authored-by: Darius Clark <[email protected]>

Author: P1R

Cargo.lock

@@ -9,10 +9,9 @@ license = "MIT"
 release = false
 
 [dependencies]
-async-std = { version = "1.12", features = ["attributes"] }
-async-trait = "0.1"
+tokio = { version = "1.37.0", features = ["full"] }
 futures = { workspace = true }
-libp2p = { path = "../../libp2p", features = ["async-std", "dns", "dcutr", "identify", "macros", "noise", "ping", "relay", "rendezvous", "tcp", "tokio","yamux"] }
+libp2p = { path = "../../libp2p", features = ["identify", "noise", "tcp", "tokio", "yamux"] }
 tracing = { workspace = true }
 tracing-subscriber = { workspace = true, features = ["env-filter"] }
 

examples/identify/Cargo.toml

@@ -25,14 +25,14 @@ use libp2p::{core::multiaddr::Multiaddr, identify, noise, swarm::SwarmEvent, tcp
 use std::{error::Error, time::Duration};
 use tracing_subscriber::EnvFilter;
 
-#[async_std::main]
+#[tokio::main]
 async fn main() -> Result<(), Box<dyn Error>> {
     let _ = tracing_subscriber::fmt()
         .with_env_filter(EnvFilter::from_default_env())
         .try_init();
 
     let mut swarm = libp2p::SwarmBuilder::with_new_identity()
-        .with_async_std()
+        .with_tokio()
         .with_tcp(
             tcp::Config::default(),
             noise::Config::new,