10.5 birthday sync not working

Steps to reproduce

1. Create a user with birthday
2. Delete this user
3. Go to owncloud server and type: sudo -u www-data ./occ dav:sync-birthday-calendar
4. Sync the client, the birthday of the deleted user is already available

Expected behaviour

With server 10.4 this workflow works very fine and all birthdays were fixed, after call the occ command.

Actual behaviour

In server 10.5 the birthdays doesn't sync correct

Server configuration

Operating system: debian buster

Web server: apache2

Database: mariadb

PHP version: 7.3.19

ownCloud version: 10.5

Updated from an older ownCloud or fresh install: upgrade from 10.4 to 10.5

List of activated apps:

Enabled:

• activity: 2.5.3
• calendar: 1.6.4
• comments: 0.3.0
• configreport: 0.2.0
• contacts: 1.5.5
• customgroups: 0.6.0
• dav: 0.6.0
• federatedfilesharing: 0.5.0
• federation: 0.1.0
• files: 1.5.2
• files_external: 0.7.1
• files_mediaviewer: 1.0.3
• files_sharing: 0.13.0
• files_trashbin: 0.9.1
• files_versions: 1.3.0
• firstrunwizard: 1.2.0
• gallery: 16.1.1
• market: 0.6.0
• notifications: 0.5.2
• provisioning_api: 0.5.0
• systemtags: 0.3.0
• tasks: 0.9.7
• templateeditor: 0.4.0
• updatenotification: 0.2.1
  Disabled:
• encryption
• external
• user_external

Are you using encryption: no

Start by reproducing the reported upgrade scenario and running occ dav:sync-birthday-calendar on ownCloud 10.5, then trace the DAV birthday-sync entry point and compare its behavior with 10.4. Done means deleted users' birthdays are removed or corrected after the command and remaining birthdays sync correctly.