Update title for Sync to include (beta)

[bsclifton]

Fixes brave/brave-browser#3079

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Windows
  • macOS
  • Linux
• Verified that these changes pass automated tests (npm test brave_unit_tests && npm test brave_browser_tests) on
  • Windows
  • macOS
  • Linux
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone

Test Plan:

1. With Sync disabled, visit chrome://sync/
2. Verify title for Sync includes (beta)
3. Enable sync
4. Verify title for Sync includes (beta)

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

[GeetaSarvadnya]

@rebron Step1, should it be With Sync Enabled, visit chrome://sync/?

[kjozwiak]

@rebron Step1, should it be With Sync Enabled, visit chrome://sync/?

I think what @bsclifton meant is visiting brave://sync while there's no sync chain and making sure that the title displays the new Beta string. Once that's verified, create a sync chain and make sure that the title still correctly uses Beta.