[items] Fix `time.ZonedDateTime` not working as command/state update

[florian-h05]

Reported on the community https://community.openhab.org/t/converting-rules-dsl-to-jsrule-ecma2021-datatype-problems/142655/12?u=florian-h05.

Signed-off-by: Florian Hotze florianh_dev@icloud.com