fix(ROS): Document hide-download option on files

[nickvergessen]

• Feature was added between Talk and Richdocuments as part of the summit release, so that Talk does not show the download button when the share was down with "hide download".
• Ref feat(sharing): Allow richdocuments to hide-download for public talk share links spreed#15095
• Ref feat: Add option to set secure view for public talk shares richdocuments#4772

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)

[nickvergessen]

/backport to stable31