ja-jp: Replace deprecated apt-key

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What does this MR do and why?

The Japanese translation is outdated in two points:

• apt-key is deprecated; see !201435 (merged)
• PostgreSQL-16 is required for GitLab 18.0

References

• !201435 (merged)
• 62ccdf86 Revisions to PostgreSQL requirements
• 03713868 Add respective Helm chart version to PostgreSQL req.
• 5f705ff4 Update PostgreSQL docs for version 16
• 303c4f53 Bump minimum required PostgreSQL version to 16
• 39562130 PostgreSQL version support and tunables

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