Fix sshd port configured test failing on ubuntu base image due to permission errors

[Copilot]

grep -r 'Port 2222' /etc/ssh/ recursively hits SSH host private key files (ssh_host_*_key) which are root-readable only. GNU grep exits with code 2 (error) when it encounters permission denied — even when the pattern is found — causing the test to fail.

Changes

• test/sshd/test.sh: Narrow the grep target to only the sshd config locations instead of the entire /etc/ssh/ directory

- check "sshd port configured" bash -c "grep -r 'Port 2222' /etc/ssh/"
+ check "sshd port configured" bash -c "grep -r 'Port 2222' /etc/ssh/sshd_config /etc/ssh/sshd_config.d/"

Original prompt

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This section details on the original issue you should resolve

<issue_title>Test for sshd feature fails on mcr.microsoft.com/devcontainers/base:ubuntu</issue_title>
<issue_description>See: https://github.com/devcontainer-community/devcontainer-features/actions/runs/23401024666/job/68074354934#logs

[2026-03-22T11:16:46.606Z] Container started
🚀 Launched container.
>  containerId:          f89df615d6cca11b68caacde18b3b78f76a53633519db5993ff174344f3d733e
🏃 Starting test(s)...
🧪 Starting 'sshd' tests...
🔄 Testing 'sshd installed'

/usr/sbin/sshd
✅  Passed 'sshd installed'!
🔄 Testing 'openssh version'

OpenSSH_9.6p1 Ubuntu-3ubuntu13.15, OpenSSL 3.0.13 30 Jan 2024
✅  Passed 'openssh version'!
🔄 Testing 'sshd port configured'

grep: /etc/ssh/ssh_host_ed25519_key: Permission denied
grep: /etc/ssh/ssh_host_rsa_key: Permission denied
/etc/ssh/sshd_config.d/devcontainer.conf:Port 2222
grep: /etc/ssh/ssh_host_ecdsa_key: Permission denied
❌ sshd port configured check failed.
🧪 Executing duplicate test for feature 'sshd'...
⚠️ Skipping duplicate test for sshd because '/home/runner/work/devcontainer-features/devcontainer-features/test/sshd/duplicate.sh' does not exist.
🧹 Cleaning up 1 test containers...
🧹 Removing container f89df615d6cc...
  ================== TEST REPORT ==================
❌ Failed:      'sshd'
Error: Process completed with exit code 1.
```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes Test for sshd feature fails on mcr.microsoft.com/devcontainers/base:ubuntu #161

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