remove opacity from new tab button

[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 #5518

Test Plan:

Make sure the new tab button is dark enough to not look disabled. Like this screenshot:

instead of this:

[bsclifton]

❤️