Draft: Warn that hosts file may be ignored by runner in docs

What does this MR do?

Adds a warning that due to golang bug the /etc/hosts file may be ignored by a runner if /etc/nsswitch.conf file is missing

Related issues

#27568 (closed) Possibly related: #4855

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• Follow the Documentation Guidelines and Style Guide.
• If you have developer access or higher (for example, GitLab team members or Core Team members)
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When applicable:

• Update the permissions table.
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• Add GitLab's version history note(s).
• Add/update the feature flag section.
• If you're changing document headings, search docs/* for old headings and replace them with the new ones to avoid broken anchors.

Review checklist

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1. Primary Reviewer

• Review by a code reviewer or other selected colleague to confirm accuracy, clarity, and completeness. This can be skipped for minor fixes without substantive content changes.

2. Technical Writer

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