Fix `port_getn` calling. #4457

Job	Run time
Check selected Tier 3 platforms (nightly)	3m 47s
Check (stable)	6m 8s
Check nightly-only targets (nightly)	22s
Check --no-default-features (nightly)	53s
Check (nightly)	6m 13s
Check (1.63)	10m 51s
Rustfmt	5s
Test rustix_use_experimental_asm (powerpc64le-linux)	1m 9s
Test rustix_use_experimental_asm (s390x-linux)	1m 4s
Test (ubuntu)	43s
Test use-libc (ubuntu)	35s
Test (ubuntu-20.04)	45s
Test use-libc (i686-linux)	52s
Test (i686-linux)	59s
Test use-libc (aarch64-linux)	54s
Test (aarch64-linux)	1m 4s
Test use-libc (powerpc64le-linux)	1m 5s
Test (powerpc64le-linux)	1m 0s
Test use-libc (riscv64-linux)	58s
Test (riscv64-linux)	1m 0s
Test use-libc (s390x-linux)	1m 4s
Test (s390x-linux)	1m 3s
Test use-libc (arm-linux)	56s
Test (arm-linux)	59s
Test (ubuntu-stable)	36s
Test (i686-linux-stable)	1m 9s
Test (aarch64-linux-stable)	1m 20s
Test (riscv64-linux-stable)	59s
Test (s390x-linux-stable)	51s
Test (powerpc64le-linux-stable)	57s
Test (arm-linux-stable)	1m 3s
Test (ubuntu-1.63)	2m 33s
Test (i686-linux-1.63)	2m 40s
Test (aarch64-linux-1.63)	2m 48s
Test (riscv64-linux-1.63)	3m 0s
Test (s390x-linux-1.63)	3m 6s
Test (powerpc64le-linux-1.63)	2m 48s
Test (arm-linux-1.63)	2m 42s
Test (macos-latest)	30s
Test (macos-13)	1m 7s
Test (windows)	52s
Test (windows-2019)	1m 11s
Test (musl)	50s
	1h 15m 31s

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