Update rewards onboarding check for JP

[deeppandya]

Resolves brave/brave-browser#28221

Submitter Checklist:

• I confirm that no security/privacy review is needed, or that I have requested one
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally:
  • npm run test -- brave_browser_tests, npm run test -- brave_unit_tests wiki
  • npm run lint, npm run presubmit wiki, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

[sujitacharya2005]

This color is used in many places. Like in tipping panel. May be better to create new color.

[SergeyZhukovsky]

++

[LaurenWags]

Verified on Google Pixel 3 XL with Android 12 running 1.50.21.

• Verified STR fom onboarding in Japan region shows auto contribution slide brave-browser#28221 (comment)

Case 1:

• Device is set to US
• Selected Japan as country
• Confirmed no "Auto Contribution" slide in onboarding
• Confirmed bitFlyer is the only custodian option

Device	Geo Selection	Onboarding	Onboarding	Onboarding	Onboarding	Onboarding	brave://rewards page	Custodian

Case 2:

• Device is set to Japan
• Selected Japan as country
• Confirmed no "Auto Contribution" slide in onboarding
• Confirmed bitFlyer is the only custodian option

Device	Geo Selection	Onboarding	Onboarding	Onboarding	Onboarding	Onboarding	brave://rewards page	Custodian