mirage/mirage: PR #1640: tests/functoria: fix differences between OCaml 4 and 5

@714deb0

Stages:

• 🟠 x86_64-debian-13-4.14
• 🟠 arm64-debian-13-4.14
• 🟠 x86_64-debian-13-5.3
• 🟠 arm64-debian-13-5.3
• ❌ x86_64-debian-13-5.4 (1m56s)
• 🟠 arm64-debian-13-5.4

History:

• 09/06/2026 11:01 ❌ @c046e73 (17m39s)
• 09/06/2026 11:00 🟠 @e968a28
• 09/06/2026 10:58 ❌ @714deb0 (1m56s)