Block script icon is off location when URL bar is hidden

[jkup]

• 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).

Fix #4007

Test Plan:

Experiment with both bookmarking and blocking scripts on websites and make sure both icons look correct on the top of the browser.

Auditors @diracdeltas @bradleyrichter

Also, @bradleyrichter I noticed some code in there that looks like maybe those icons used to be somewhat see through and then bolden on hover? Is that still desired?

[diracdeltas]

@jkup yup the icons should darken on hover so that it's obvious they are clickable.

[diracdeltas]

lgtm but please re-add the hover darkening

[jkup]

@diracdeltas thanks! updated.

[diracdeltas]

++ thanks