Removed link's underline from settings UI

[simonhong]

fix brave/brave-browser#26091

Below upstream's change enabled underline.
https://chromium-review.googlesource.com/c/chromium/src/+/3855278

WebUI: Decorate links with underline

This is part 1 of decorating all links and all buttons that look like links with the underline to help users better differentiate between normal text and actionable links. This CL updates links on Settings, Extensions, Management, Downloads, and Welcome, as well as updating a couple of global WebUI styles.

Resolves

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, npm run lint, 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:

See the linked issue

[emerick]

LGTM

[petemill]

Thanks for the fix. I think it's better if we put the css file in brave/browser/resources/settings and phase out page_specific, which was more of a convenience place to place overriding resources for chromium WebUIs where we haven't yet setup our places to inject modifications.

[kjozwiak]

Verification PASSED on Win 11 x64 using the following build(s):

Brave | 1.47.14 Chromium: 107.0.5304.62 (Official Build) nightly (64-bit)
-- | --
Revision | 1eec40d3a5764881c92085aaee66d25075c159aa-refs/branch-heads/5304@{#942}
OS | Windows 11 Version 22H2 (Build 22621.675)

Went through the STR/Cases outlined via brave/brave-browser#26091 (comment) and ensured that links weren't being underlined via brave://settings as per the following:

Example	Example	Example