Stable v2.10.2

• fix(i18n): say the staging certificate is the address's own in the Turkish note
• feat(dashboard): add a curated What's-new note for 2.9.107 in all 15 languages
• feat(dashboard): translate the 2.10.1 What's-new notes into 13 more languages
• docs: describe the mail envelope and correct what today's release made untrue
• fix(release): keep the trailing newline when restoring the testing version