docs: bump lastUpdated to 2026-07-13 for guides merged but not yet deployed (#385)

Guides merged into develop on 2026-07-10, pending the next production
deploy — align their lastUpdated with the deploy date:
- web-cloud/email locked-for-spam (7 locales, #363)
- account/billing best-practices, ovh-orders, update-vat-rate (FR, #369)
- web-cloud/phone-and-fax fax + voip guides (FR, #379/#380)