Update text colour on rewards onboarding

[deeppandya]

Resolves brave/brave-browser#13800

Submitter Checklist:

• There is a ticket for my issue.
• Used Github auto-closing keywords in the commit message.
• Wrote a good PR/commit description
• 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, npm run lint, npm run gn_check, npm run tslint
• Ran git rebase master (if needed).
• Requested a security/privacy review as needed.

Reviewer Checklist:

• 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:

[SergeyZhukovsky]

++

[kjozwiak]

Verification PASSED on Samsung S10+ running Android 10 using the following build:

1.21.39 CR: 88.0.4324.96

Example Text Link Fixed	Example Text Link Fixed

Alignment Improved #1	Alignment Improved #2

After speaking with @codybanxs & @deeppandya, the "light grey text" that's exampled via brave/brave-browser#13800 (comment) will be addressed in the UI revamp in 1.21.x.

[kjozwiak]

@deeppandya @codybanxs I wouldn't consider this a blocker either way but Alignment Improved #2 still looks a but unaligned at the bottom where the blue text and the grey bottom text have a small offset. We can create a new issue for the above as brave/brave-browser#13800 was technically about fixing the text so it doesn't look like a hyperlink.

[deeppandya]

@deeppandya @codybanxs I wouldn't consider this a blocker either way but Alignment Improved #2 still looks a but unaligned at the bottom where the blue text and the grey bottom text have a small offset. We can create a new issue for the above as brave/brave-browser#13800 was technically about fixing the text so it doesn't look like a hyperlink.

@kjozwiak thank you mentioning it. I will definitely take a look and update it in the follow up issue.

[kjozwiak]

Sounds good @deeppandya 👍 Created brave/brave-browser#13909 re: alignment issues.