Removes two plugin tests that aren't actually doing anything useful.

When they were added they were testing v2-embedding plugins in a v1-embedding app, but support for creating v1-embedding apps--and the environment variable that these tests were using to, in theory, trigger them--was removed several years ago in #61203. That means that these tests are in practice exact duplicates of the copies just above without the ennvironment variables.

Fixes https://github.com/flutter/flutter/issues/122200