Fix sortableTable hover effect and searchTab onClick

[darkdh]

• 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:

fix #4099

Auditors: @bbondy

Test Plan:

1. Go to "about:preferences#search"
2. There should be hover effect when hovering on row
3. Should be able to swtch default search engine

[bbondy]

++