fix(files_external) Redact sensitive S3 values

[joshtrichards]

Summary

While troubleshooting another matter, noticed these weren't being redacted

• Adds S3 key / secret / bucket to list of values redacted automatically when dumping files_external config via occ
• Adjusted the redaction string to match the one we use for occ config:list system

Probably not critical enough to backport to stable28.

TODO

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)