[ads] Brave News Inline ads orphaned events are logged as purged even when there were none

[btlechowski]

Note: this is only logging related. Purging works properly

Steps to reproduce

1. Clean profile
2. Run Brave with

--enable-logging=stderr --vmodule="*/variations/*"=6,"*/bat-native-ledger/*"=6,"*/brave_rewards/*"=6,"*/bat-native-ads/*"=6,"*bat-native-confirmations/*"=6,"*/brave_ads/*"=9,"*/brave_user_model/*"=6,"*/bat_ads/*"=6,"*/whats_new/*"=9 --variations-server-url=https://variations.bravesoftware.com/seed1 --rewards=staging=true,debug=true --use-dev-goupdater-url --enable-features=ShouldAlwaysRunBraveAdsService,ShouldAlwaysTriggerBraveSearchResultAdEvents,ShouldLaunchBraveAdsAsInProcessService,ShouldSupportSearchResultAds,ShouldAlwaysTriggerBraveNewTabPageAdEvents,CustomNotificationAds,NotificationAds:default_ads_per_hour/5,InlineContentAds:maximum_ads_per_day/1

3. Open NTP
4. Enable Brave News Inline ad
5. View an Brave news inline ad
6. Close the tab which contain the viewed ad

Actual result

Logs show orphaned events were purged

Expected result

Logs are improved.

Reproduces how often

Easily reproduced

Brave version (brave://version info)

Brave	1.68.29 Chromium: 125.0.6422.60 (Official Build) nightly (64-bit)
Revision	00e032de86c92faa949ed70f87fa29f9ef10aad6
OS	Linux

cc @tmancey @aseren