Remove top:1px from .urlbarForm > *

[luixxiul]

Closes #7805

The fix is no longer necessary as the header design became flat thanks to #7546 and #7739

Auditors:

Test Plan: make sure the URL bar looks like #7805 (comment)

• 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).

Test Plan:

[bradleyrichter]

sounds good