Omit datetime from JSON conversion that converts from strings

[Migaroez]

Prerequisites

• I have added steps to test this contribution in the description below

Fixes #19360

Description

This PR removes jsonobject of type text to DateTime conversion.
I think we can do this as none of the valueEditors that touch deal with Date(time) values require the object passed in to be of type DateTime.
@ronaldbarendse Could you give your 2 cents regarding deploy and the following issue pr?
#16732

Testing

See reproduction steps in 19360, test both in and outside of blocks/elements
See if you can find something that breaks with this code gone. I couldn't

[AndyButland]

Just to add some further detail: this was added in #13537 - the updates from @ronaldbarendse in his PR linked above was just to extend the date conversion to handle DateTimeOffset as well. @Zeegaan - you had a hand in this PR that actually adds this class - quite some time back - but maybe you recall some background and whether this is a concern to remove?

[AndyButland]

I don't see any issues with setting, persisting and retrieving dates following this change. Have checked:

• Setting values in a date picker on a document
• Setting values in a date picker in a block
• Setting values in a date picker in a block within an RTE
• Setting scheduled publishing

Can also confirm the linked issue is resolved.

Holding off on the "Approve" button for now in case of further feedback or concern on removing this update.

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I note one failing E2E test too. I've re-triggered it in case it's a flaky one but if it fails a second time would be worth investigating to see if this update is related.