NightwatchBrowser type is deprecated

[Jane Sandberg]

I noticed this in VS codium: if you open a nightwatch test (for example, Open-ILS/src/eg2/nightwatch/src/staff/admin/local/carousels.spec.ts), you get a note that the NightwatchBrowser type is deprecated, and that you should use NightwatchAPI instead.

I think that all that is required is to simply Find and Replace NightwatchBrowser -> NightwatchAPI.

Success criteria would be:
* We don't use the deprecated NightwatchBrowser type.
* VS Codium/VSCode don't complain about this deprecation when you open the browser.
* The nightwatch tests still compile

This is on today's main branch.