metamask notification is missing the caret extending into trusted UI

[diracdeltas]

we show a caret on Brave notification bars to indicate that they are "trusted UI" (not spoofable by a web page). the metamask notification is missing it, but permission notifications have it.

^ note the small triangle pointing into the Google tab title area

either it should have the caret or it should appear above the tab bar

[kjozwiak]

STR/Test Case:

• create a new tab and visit https://ethwaterloo.herokuapp.com/, ensure that you receive a "Dapp" notification
• create a new tab and visit https://www.stateofthedapps.com/dapps/adchainregistry, ensure that you receive a "Dapp" notification
• create a new tab and visit https://tokenfactory.surge.sh, ensure that you receive a "Dapp" notification
• create a new tab and visit https://leeroy.io/, ensure that you receive a "Dapp" notification
• click through each tab and ensure that the selector caret is correctly pointing to the tab that's currently being selected (example in metamask notification is missing the caret extending into trusted UI #11536 (comment))
• ensure that the URL under the notification message and the caret selector are pointing to the correct website