[FIX] digest: resolve unmet dependency on resource module

This commit fixes the following bug:
* On a new DB, install account
* Settings > Technical > Email > Digest emails
* Open Weekly Digest, set Next Send Date to current day
* Settings > Technical > Scheduled Actions > Digest Emails
* Run manually

AttributeError: 'res.company' object has no attribute
'resource_calendar_id'

The field resource_calendar_id is provided by the module resource

closes odoo/odoo#28239

addons/digest/__manifest__.py

@@ -10,7 +10,8 @@ Send KPI Digests periodically
     'version': '1.0',
     'depends': [
         'mail',
-        'portal'
+        'portal',
+        'resource',
     ],
     'data': [
         'security/ir.model.access.csv',