Disable SKU SDK on Linux by default

[bsclifton]

Disable SKU SDK on Linux by default. VPN is not available for Linux yet - so it's safe to turn off.

This fixes the crash that we're seeing. I'll open a specific issue for that problem; we still need to troubleshoot why an invalid instruction is executed on Linux when this is enabled.

Resolves brave/brave-browser#23140

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:

1. Have an official build with this code
2. Be on Linux
3. Login to account.brave.com
4. It should work and not crash

[kjozwiak]

Verification PASSED on Pop OS 22.04 x64 using the following build(s):

Brave | 1.41.61 Chromium: 103.0.5060.42 (Official Build) nightly (64-bit) 
--- | ---
Revision | de0d840bf9439c31bd86bf74f065c31fdf9b208d-refs/branch-heads/5060@{#667}
OS | Linux

I couldn't reproduce the original issue using either 1.41.12 or 1.41.49 but verified that the above is still working with the latest Nightly using the STR/Cases outlined via brave/brave-browser#23140 (comment) & #13702 (comment). @wknapik also verified the the issue was fixed on Nightly as per brave/brave-browser#23140 (comment).