Some users are not served ads due to failure to initialize Brave Ads when migrating to database schema 21

[tmancey]

Description

Users are not served ads due to failure to initialize Brave Ads when migrating to database schema 21

Steps to Reproduce

1. Install 1.23.21
2. Trigger a conversion
3. Quit the browser
4. Upgrade to 1.37.7 or newer

Actual result:

Successfully initialized ads does not appear in the console log and ads are no longer served to users

Expected result:

Successfully initialized ads should appear in the console log

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

Version/Channel Information:

• Can you reproduce this issue with the current release? Yes
• Can you reproduce this issue with the beta channel? Yes
• Can you reproduce this issue with the nightly channel? Yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? N/A
• Does the issue resolve itself when disabling Brave Rewards? N/A
• Is the issue reproducible on the latest version of Chrome? N/A

Miscellaneous Information:

[btlechowski]

Verification passed on

Brave	1.38.119 Chromium: 101.0.4951.67 (Official Build) (64-bit)
Revision	8888ee7a24e2c36661ddb9536c35b7d4852a3a98-refs/branch-heads/4951@{#1230}
OS	Ubuntu 18.04 LTS

Verified fixed:

Verified got a notification ad

[8920:8920:0517/155932.581290:VERBOSE1:ad_notification_serving.cc(142)] Found 10 eligible ads
[8920:8920:0517/155932.581570:VERBOSE1:ad_notification_serving.cc(261)] Serving ad notification:
  uuid: 9342d93c-636d-48e4-9485-c7c0b90096ef
  creativeInstanceId: 759e8fee-c930-4518-b003-9e62e322eea8
  creativeSetId: ffd12748-001c-417e-b8a3-d36bceb9f032
  campaignId: 85ddd55c-3cc8-4c25-9ea4-8d5a2d3d1279
  advertiserId: bfac6e60-a86e-44d7-901b-49df77e5cae3
  segment: business
  title: Grow Your Crypto up to 3x
  body: Leverage your crypto up to 3 times with the Nexo Booster!
  targetUrl: https://nexo.io/booster?utm_source=brave&utm_medium=fixed&utm_campaign=brave_boosterpush_apr22

Got paid for the ad:

[8920:8920:0517/155946.142575:VERBOSE1:confirmations.cc(299)] Successfully redeemed unblinded token for ad_notification with confirmation id 6e69f68b-6b67-4a1a-a275-52407227ff2a, transaction id 5e0c4629-2a3a-419d-a6c4-7d7ff7a327e9, creative instance id 759e8fee-c930-4518-b003-9e62e322eea8 and view.