docs: switch datepicker examples to Luxon

[crisbeto]

Switches the live datepicker examples that were using Moment to use Luxon instead. This simplifies our build setup and avoids having to load in locale data.

Fixes #31998.

[rbalet]

Hey @crisbeto. i had a look at the following commit, and I saw the following

By default the LuxonDateAdapter creates dates in your time zone specific locale. You can change
the default behaviour to parse dates as UTC by passing useUtc: true into provideLuxonDateAdapter:

But this doesn't seems to be true, as provideLuxonDateAdapter does only accept MatDateFormats as argument.
Do you see another option to for setting the UTC ?