This commit removes the main MP2 migration class and its test class. It
also removes two SQL files that were used in the test class. One of
those files executed the following query:
`SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO"`
Removing this query made the tests inside SubscriberSegmentTest fail
when running the whole integration test suite. To work around this, I
added the above mentioned query to SubscriberSegmentTest. I'm not sure
why this test class fails without this query when running all the tests
but it doesn't when it is executed alone. Probably there is another test
class changing the SQL_MODE. Since SubscriberSegmentTest is a test class
for a Paris model that we will eventually remove, I decided it was not
necessary to investigate this further.
[MAILPOET-4376]
