fix search favicon path on windows

[diracdeltas]

for some reason, the windows path has an extra ../ prefix compared to
mac so the favicon doesn't load. this works around the issue by removing
a ../ on windows.

fix #14653

Test Plan:

1. open new tab
2. hit :g in the urlbar
3. the search favicon should load on all platforms

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).
• 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. (Ask a Brave employee to help if you cannot access this document.)

Test Plan:

Reviewer Checklist:

• Request a security/privacy review as needed if one was not already requested.

Tests

• Adequate test coverage exists to prevent regressions
• Tests should be independent and work correctly when run individually or as a suite ref
• New files have MPL2 license header

[srirambv]

++ tested manually on Windows. shows correct favicon

[bsclifton]

master 3d830d7
0.24.x 01a1518
0.23.x 7f40503