Remove the multi-db SQL test data.
Remove the multi-db SQL test data.

The test data for SQLite contained a `multi_db` series of SQL
statements. These were used a long while back to test evolutions when
multiple databases were involved. They're no longer needed, as the
appropriate tests are just run against the other series of SQL
statements. This change just removes them.

Testing Done:
All unit tests pass.

Reviewed at https://reviews.reviewboard.org/r/9581/

beanbaginc/django-evolution