Admin Instructor List: Make Search Live instead of requiring a button click or enter

With https://github.com/classtranscribe/FrontEnd/pull/806 we are now using a React State to track the text box. Based on this, we can make the search happen 'live' with every state change. That way we won't need to even hit enter or click the button.

React is quite smart with vdom refreshes around this kind of search, so the performance should be quite good.