Remove browser test suite

[Jameskmonger]

The browser test suite is no longer functional

PhantomJS has not been supported since 2018 so I suggest we remove this test suite.

I'm not convinced there's much value in a specific set of browser tests anyway, given that our bundling mechanisms aren't necessarily the same as our users'.

[Jameskmonger]

Inviting feedback on this for the next few days, in the absence of any feedback I will be removing the faulty pipeline to unblock PR #1531

cc @inversify/maintainers @inversify/collaborators @PodaruDragos @dcavanagh

[PodaruDragos]

+1 from me. If we ever need browser tests, we can always just use a different maintained framework like puppeteer.

[remojansen]

+1 For context when the browser tests were added was a time in which we still had IE and browser compatibility was still a very big issue. I don't think is relevant today.

[acald-creator]

+1 from me, no argument here

[Jameskmonger]

Thanks for the feedback @PodaruDragos @remojansen @acald-creator

I will get on this this morning 😄