Get the request time to set on the updated entity in LayoutParagraphsBuilderForm

Problem/Motivation

LayoutParagraphsBuilderForm uses time() to set the changed time on the entity.

It should use the request time from the time service instead. The current code may set a (slightly) incorrect time.

(The MR at 🐛 Experimental widget displays the original language on translation Needs work has code for this which could be used here, but it's conflicting with the main branch.)

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes