Remove region support for Ads as CDN now controls catalog for each region

[tmancey]

fixes brave/brave-browser#3752

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Windows
  • macOS
  • Linux
• Verified that these changes pass automated tests (npm test brave_unit_tests && npm test brave_browser_tests) on
  • Windows
  • macOS
  • Linux
• Verified that all lint errors/warnings are resolved (npm run lint)
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone

Test Plan:

Test that Ads are shown by using a VPN to set your location to one of the supported regions. And that Ads are not shown when setting your location to one of the unsupported regions.

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

[NejcZdovc]

@tmancey how can regular Joe like me from Slovenia test ads if local will be determinate via CDN and ads are not available here? The only thing that I can think of is VPN.

[tmancey]

@NejcZdovc Only way is using a VPN

[srirambv]

I am not seeing any ads on Linux when device region is set to Canada, and using a VPN(US node) still doesn't seem to trigger ads.

Console shows

Catalog shows region as US

@mbacchi mentioned in slack that he was able to see ad on Linux however when I try with/without VPN I am still not able to see any ads on Linux. When spoke to @tmancey on call he mentioned this PR fixes the issue of region and not seeing ads. @jsecretan we should probably get this reviewed soon and have it uplifted to dev.