Fix import guards in NIOSSHServer #79

Job	Run time
Unit tests / Construct unit test matrix	3s
Cxx interop / Construct Cxx interop matrix	3s
macOS tests / Construct Darwin matrix	3s
Benchmarks / Construct Benchmarks matrix	3s
Soundness / API breakage check	3m 10s
Soundness / Broken symlinks check	5s
Soundness / Documentation check	2m 27s
Soundness / Python lint check	8s
Soundness / Format check	37s
Soundness / License headers check	4s
Soundness / YAML lint check	6s
Soundness / Unacceptable language check	4s
Soundness / Shell check	31s
macOS tests / Xcode 26 beta 1	5m 15s
macOS tests / Xcode 16.3	5m 53s
macOS tests / Xcode 16.2	3m 51s
Cxx interop / Cxx interop / Linux (nightly-next)	2m 45s
Cxx interop / Cxx interop / Linux (nightly-main)	2m 33s
Cxx interop / Cxx interop / Linux (6.0)	2m 7s
Cxx interop / Cxx interop / Linux (5.10)	1m 50s
Cxx interop / Cxx interop / Linux (6.1)	2m 4s
Unit tests / Unit tests / Linux (5.10)	1m 54s
Unit tests / Unit tests / Linux (6.0)	2m 12s
Unit tests / Unit tests / Linux (nightly-main)	2m 45s
Unit tests / Unit tests / Linux (6.1)	2m 14s
Unit tests / Unit tests / Linux (nightly-next)	2m 51s
Benchmarks / Benchmarks / Linux (nightly-next)	5m 40s
Benchmarks / Benchmarks / Linux (6.0)	5m 25s
Benchmarks / Benchmarks / Linux (nightly-main)	5m 43s
Benchmarks / Benchmarks / Linux (5.10)	5m 1s
Benchmarks / Benchmarks / Linux (6.1)	4m 55s
	1h 12m 22s

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