Old collections / blank state do not have the common property "date modified"

[RafaPolit]

When this functionality was implemented, the blank state fixtures, the puppeteer, nor old collections got updated with this value on the templates in database.

Look into the need to actually create a migration to include this in all templates.

[txau]

@RafaPolit related to this: https://github.com/huridocs/uwazi/issues/4222

Apparently there are no side effects and when the entity is edited it gets a "data modified". Is it worth to fix it?