MaximumEntriesInAdsShownHistory is not respected

[btlechowski]

Follow up to #5863
brave/brave-core@517ce8d
Max is set to 560, I was able to show 3000 entries

Steps to Reproduce

1. Clean profile
2. Enable rewards
3. View an ad
4. Close Brave
5. copy generate_ads_history.py to [PROFILE]\Default\ads_service\
6. Run generate_ads_history.py
7. Run Brave
8. Open brave://rewards
9. Reload the page few times to shown the generated ads history

generate_ads_history.zip

Actual result:

3000 entries are shown

Expected result:

Max 560 entries are shown per brave/brave-core@517ce8d

Reproduces how often:

100% repro rate

Brave version (brave://version info)

Brave	1.4.85 Chromium: 80.0.3987.87 (Official Build) beta (64-bit)
Revision	449cb163497b70dbf98d389f54e38e85d4c59b43-refs/branch-heads/3987@{#801}
OS	Windows 7 Service Pack 1 (Build 7601.24544)

cc @brave/legacy_qa @tmancey @rebron

[tmancey]

@btlechowski can you please retest with 559 ads and then viewing 2 ads, to see if the limit is now 590. The code will not remove ads past 590 as the logic is if exceeding the limit after adding an ad we remove the oldest ad.