CRM-10606 Remove specific code for upgrade from 2.0 to 2.1

cf. http://issues.civicrm.org/jira/browse/CRM-10606

I removed some old code to allow upgrade from 2.0 to 2.1 (when first version of multilingual was introduced). This piece of code create problems in multilingual civi migration (with aegir/drush anyway).

It seems very unlikelly that someone do the migration from version prior than 2.1 to 4.3 directly so i think we can safely remove this code.