chore(ci): Remove legacy TCP integration tests

Prompted by #11112 (comment)

I don't really have a strong opinion here, so opening up to solicit
others. Does anyone see value in these tests? Or do we think we have
sufficient coverage already of the behavior here? These tests were
introduced very early on in Vector's history, so it seems plausible that
they may have outlived their usefullness.

The `merge_and_fork` one, in particular, has shown up as flakey in the
past.

Signed-off-by: Jesse Szwedko <jesse@szwedko.me>