chore(examples): remove unused dependency from rendezvous (#5580)

## Description

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Following on issue #4449 
refactor: remove unnecesary dependencies rendezvous example (async-std)
## Notes & open questions

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in the rendezvous example there where unnecessary dependencies in the
Cargo.toml

## Change checklist

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

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crate versions if needed. See
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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: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Author: P1R

Cargo.lock

@@ -9,10 +9,8 @@ license = "MIT"
 release = false
 
 [dependencies]
-async-std = { version = "1.12", features = ["attributes"] }
-async-trait = "0.1"
 futures = { workspace = true }
-libp2p = { path = "../../libp2p", features = [ "async-std", "identify", "macros", "noise", "ping", "rendezvous", "tcp", "tokio", "yamux"] }
+libp2p = { path = "../../libp2p", features = ["identify", "macros", "noise", "ping", "rendezvous", "tcp", "tokio", "yamux"] }
 tokio = { workspace = true, features = ["rt-multi-thread", "macros", "time"] }
 tracing = { workspace = true }
 tracing-subscriber = { workspace = true, features = ["env-filter"] }