mirage/mirage: PR #1568: config.ml: Make deprecation warnings non-errors

@4bcf7a7

Stages:

• 🟠 x86_64-debian-10-4.13 (6m18s)
• ✔️ arm64-debian-10-4.13 (6m43s)

History:

• 04/10/2024 09:03 ✔️ @127dcfe (3h06m)
• 03/10/2024 09:29 ✔️ @577d89d (34m57s)
• 03/10/2024 08:24 ✔️ @43a9cec (7m13s)
• 03/10/2024 07:40 ✔️ @b1e27f3 (7m38s)
• 02/10/2024 14:41 ✔️ @2fc4c26 (10m48s)
• 02/10/2024 14:30 🟠 @4bcf7a7 (6m43s)