regulace konopi: Fix deprecated import

regulace_konopi/models.py

 from django.db import models
 from django.utils.translation import gettext_lazy
-from wagtail.admin import blocks
 from wagtail.admin.edit_handlers import (
     FieldPanel,
     HelpPanel,
     MultiFieldPanel,
     StreamFieldPanel,
 )
+from wagtail.core import blocks
 from wagtail.core.fields import StreamField
 from wagtail.core.models import Page
 from wagtail.images.blocks import ImageChooserBlock