Deleting past published article makes the title not usable again for future publish

[enwee]

Steps to reproduce problem:

1. Click on Create new article button on Dashboard.
2. On the Editor page, type in Topic Title: 31Dec2020 and Sub Topic Title: 31Dec2020s
3. Click Publish
4. Click Delete article in editor page
5. Create new article with Topic Title: 31Dec2020 and Sub Topic Title: 31Dec2020s
6. Save it as draft and/or publish it
7. Observe it tries to publish as a duplicate article

[leechongren]

Suspect this is caused by delete article function only deleting from Draft collection.
Need to amend delete article route to delete from both draft and published (if exist).

[teojincheng]

Delete article in its most ideal implementation should remove the topic from the category collection.