Match font whitelist case insensitively

[pilgrim-brave]

Resolves brave/brave-browser#23093
Resolves brave/brave-browser#23541

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:

[kjozwiak]

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

Brave | 1.42.20 Chromium: 103.0.5060.53 (Official Build) nightly (64-bit)
-- | --
Revision | a1711811edd74ff1cf2150f36ffa3b0dae40b17f-refs/branch-heads/5060@{#853}
OS | Windows 11 Version 21H2 (Build 22000.739)

Test Case #1 - brave/brave-browser#23541

Launched Nightly using the following terminal/CLI switch to ensure that Griffin doesn't come into play and we're checking the browser fix as we've pushed the DisableReduceLanguage:Default study as per brave/brave-variations#292.

brave.exe --enable-logging=stderr --variations-server-url=https://variations.bravesoftware.com/seeasdsadd

Went through the STR/Cases outlined via brave/brave-browser#23541 (comment)

@brave/qa-team As discussed via Slack with @bsclifton, we'll leave brave/brave-browser#23093 opened until we start receiving feedback from users re: brave/brave-variations#292 fixing their issue.

In terms of verification, we'll change the label to QA/No on brave/brave-browser#23093 as the feature will be disabled at that point (1.40.x - Release #3) and we'll start enabling it via Griffin and monitor feedback.