fix(iroh-relay): removes deadlock in `Clients` #12112

Job	Run time
Cross Build Only (x86_64-unknown-freebsd)	44s
Android Build Only (aarch64-linux-android)	1m 3s
Android Build Only (armv7-linux-androideabi)	1m 5s
Checking docs	1m 13s
Checking fmt	31s
check_semver	3m 48s
clippy_check	2m 30s
Cross Test (i686-unknown-linux-gnu)	1m 56s
Build wasm32	26s
cargo deny	26s
codespell	3s
Minimal Supported Rust Version	1m 17s
CI Test Suite / Tests (ubuntu-latest, stable, all)	2m 47s
CI Test Suite / Tests (ubuntu-latest, stable, none)	2m 23s
CI Test Suite / Tests (ubuntu-latest, stable, default)	2m 22s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	2m 51s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	2m 18s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	2m 27s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	2m 6s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	2m 31s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	2m 16s
netsim-integration-tests / Netsim	5m 12s
	42m 15s

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