fix(iroh-net): `poll_send` should drop transmits that we dont have a … #8736

Job	Run time
check_semver	5m 3s
Cross Build Only (armv7-linux-androideabi)	1m 5s
Build wasm32	37s
Cross Build Only (aarch64-linux-android)	1m 1s
Cross Build Only (x86_64-unknown-freebsd)	1m 7s
Checking docs	1m 48s
Checking fmt	9s
Cross Build Only (x86_64-unknown-netbsd)	1m 9s
clippy_check	2m 32s
Cross Test (i686-unknown-linux-gnu)	2m 38s
Minimal Supported Rust Version	1m 53s
cargo deny	33s
Run network simulations/benchmarks	3m 32s
CI Test Suite / Tests (ubuntu-latest, stable, all)	3m 4s
CI Test Suite / Tests (ubuntu-latest, stable, none)	2m 5s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	3m 54s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	3m 53s
CI Test Suite / Tests (ubuntu-latest, stable, default)	2m 30s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	4m 8s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	3m 11s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	2m 51s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	2m 54s
	51m 37s

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