dcutr example: filename collision

[kpp]

rust-libp2p$ cargo test --workspace --no-default-features
warning: output filename collision.
The example target `client` in package `libp2p-dcutr v0.6.0 (/home/kpp/parity/rust-libp2p/protocols/dcutr)` has the same output filename as the example target `client` in package `libp2p-autonat v0.7.0 (/home/kpp/parity/rust-libp2p/protocols/autonat)`.
Colliding filename is: /home/kpp/parity/rust-libp2p/target/debug/examples/client
The targets should have unique names.
Consider changing their names to be unique or compiling them separately.
This may become a hard error in the future; see <https://github.com/rust-lang/cargo/issues/6313>.

$ rustc -vV
rustc 1.63.0 (4b91a6ea7 2022-08-08)
binary: rustc
commit-hash: 4b91a6ea7258a947e59c6522cd5898e7c0a6a88f
commit-date: 2022-08-08
host: x86_64-unknown-linux-gnu
release: 1.63.0
LLVM version: 14.0.5

[mxinden]

I don't feel strongly about the name client in either, in case anyone wants to provide a patch.