fix(api): Ignore "parsed" link and icon urls when deleting

[nickvergessen]

Tested on prod for myself after seeing that I had 73 notifications in the database but only 2 displayed in the UI.

The problem is Talk and some others don't have an icon/link stored in the database (as they might change), instead they are added on rendering, e.g. here:
https://github.com/nextcloud/spreed/blob/eb45b2eb8787207d072e5399da50f24f000df658/lib/Notification/Notifier.php#L242-L244

However Talk does this generally up front, so when it later on says "alright, the chat was read already, lets mark the notification as processed":
https://github.com/nextcloud/spreed/blob/eb45b2eb8787207d072e5399da50f24f000df658/lib/Notification/Notifier.php#L487-L498
the data is already manipulated.

Notifications app is then asked to delete the notification, but it adds the non-empty link and icon to the query, they are empty in the DB => No match => No delete

I think it's save to assume that link and icon are never used as "uniqueness" factor and therefore we can ignore them on deletion.

[github-actions]

🐢 Performance warning.
It looks like the query count of the integration tests increased with this PR.
Database query count is now 8549 was 8200 (+4.25%)
Please check your code again. If you added a new test this can be expected and the base value in tests/Integration/base-query-count.txt can be increased.

[nickvergessen]

/backport to stable28

[nickvergessen]

/backport to stable27

[nickvergessen]

/backport to stable26