Fixes ISSUE-50891. Remove obsolete InitializeCostingMigrationPreference

That modulescript was supposed to be removed in issue 41421 (20Q1). However the removal had missed to .class files.

So the modulescript was still technically present and running. Fix that by removing the leftover class files.

Note that 41421 did already add a buildvalidation to ensure the migration was ran before allowing the update.

try: https://builds.openbravo.com/view/try/job/try-init/1806/